This is aimed mostly towards new players, as many of the old standards still apply, though many old mechanisms have been modified.
So, its a brand new world and you're looking to make your mark on it! Not so fast, that shiny new build of yours may have great potential, but you're 40 HP and level 1 basic punch wont do much to get you there. There aren't any newbie zone with "Slightly Aggravated Bunnies" to grind, the wasteland is harsh. Provided below are a few tips for accelerating your leveling.
1) Invest in your Outdoorsmanship early and often. Get it up to 100, 150 if you can. Seriously, its worth it now. Even if you have a buddy with a taxi alt. canceling past encounters that would ordinarily be too tough to fight is a dandy way to earn XP, and insure you don't end up with free bullets donated to your groin. Why 100? because it allows you to go for the Ranger perk. Ranger is now a support perk, which means there's no inherent opportunity cost in taking it if you already have the skills for it. There isn't a limit to how many support perks you can maintain, unlike level perks. Ranger is a great Newbie perk, thanks to the ranger safe-house. Yes, tents now have campfires you can craft over, but the safe-house comes with a crafting bench, and several containers to fill. Set it down next to a mine or ruins and you can gather resources and craft without ever coming in contact with those pesky PCs in towns and cities. No more waiting in line to craft or having your products stolen from you before you even close your fix-boy.
2) Gather apples/mutated fruit. (Need at least 3 charisma) Don't eat them, unless you want your urine to glow in the dark, but gather them whenever you can. Nearly half of all ruins encounters will have a fruit tree (along with bountiful junk to craft BBs for sale), and some desert encounters will have up to 3 apple trees. fruit trees can provide up to 50 fruit, which weighs next to nothing. Just keep clicking away until the "apples" disappear or or you get a message saying the tree is out. I like to park new players in the ruins between hub and bone-yard. In 25 minutes, you've got yourself 1000 apples. then all you have to do is walk to hub and cash in with the poor starving orphan by the brahmin pens. Forget waiting for cows to poop, now all you need to do is start offering the kid apples and hammer "2" to continue offering one at a time. I like to keep my apples in my active hand to prevent theft, and show me how many I have left. the kid gives 5xp per fruit, so the 25 minutes for gathering + 5 minutes of shoving apples down the kids infinite gullets provides 5000XP, that's 10k experience per hour... just make sure you aren't carrying anything valuable while you're standing there blindly giving the child radiation sickness/explosively distended bowels.
3)Wasteland League, (dis)Assemble! - take your loot apart if you aren't going to use. This doesn't grant xp as of yet (they use to, and may still be again), but metal parts are still at a temporary premium and are sometimes worth more to merchants than the guns they came from. For new players, caps can be hard to come by, and with mines now limited by depletion, many players will pay caps (or precious brahmin hides) for metal parts. Just don.t make trades outside of unguarded cities. But what does making money have to do with experience?
4) Buy your way through quests. Some quests aren't intended for lowbies. They tend to have higher experience payoffs, but require a lot of goforing (go for this, get me that, etc) through territory dangerous to blue suits. Many of these quests however have simpler solutions if you have the cash. you could schlep to Klam, Reno, and BH for Kohl's books... or you could go to a library in hub or boneyard and save yourself several encounters with a PK. Similarly you could hoof it across the wastes Lilly, Elmer, Mick, Westin etc... or you could take the train, and just hop off close to your destination. Then again if you invest enough in ODM, it might be better to walk and enjoy watching your xp climb with each encounter.
5) Bluesuit it. Number one noob mistake I see is low level players gallivanting around in armor or with anything higher than low-tier weapons. You are going to die in the game. A lot. And most of the time you will not retrieve your stuff afterwords. unless you are actively looking for a fight (and at your level that's probably PvE not PvP), you should be carrying as little as possible. That spiffy new jacket buster gave you may look nice, but with your wopping 37 HP, I only need to put 1 bullet through it, regardless of AC, and it becomes mine. Not that I'd wear it, but I could sell it or dismantle it, or decorate my tent floor with it. Until you are already at or near the top of the food chain, armor is pretty much worthless unless you're fighting critters. Get a tent and leave your stuff there until you're man/woman enough to put it to good use. But again, what does this have to do with xp? Bluesuit means you have nothing to loss, except maybe 30 seconds of your time. You are liberated from fear of losing your worldly possessions, and free to fight like there's no tomorrow. Got an enemy to kill for a quest that you know could one-hit-kill you? blue suit it. you're probably going to die, but you might be able to suicide kill him with you. point-blank him with a molotov, or if your quests allows numerous attempts, keep trying to initiate combat with a target shot to the eye until eventually you crit. Water the desert with your blood if necessary, it only takes 20 seconds to respawn, and then you get that nice DO=FA experience to boot.
6) Legacy of the Questwhore. The post wipe world is ripe with new quests. many are easy, many are poorly balanced when it comes to the rewards, and some will provide support perks that essentially increase your skills/abilities without even needing to level, allowing you to use your experience and skill points more efficiently. With the exception of time limited quests, there does not appear to be any limit to the number of active quests you can take on at once, so get out there and commence ass-kissing/kicking.
7) Shit shoveling is a waste of time. seriously, you are better off letting rad scorpions poison you and getting experience off first aid. the cool-down is actually faster than waiting for cows to poop. problem is with less than 50 hp, you tend to die from the poison before your FA cools down. you are probably even better off crafting shovels for 14 xp a pop. unless you are shoveling to scrounge up enough caps for a bank account, or you've found a city deserted of other shovelers, you are wasting your time.
8) Join an NPC faction and ride their coat-tails. This is easiest with VC, but probably safest with BoS. join the faction, wander around no more than a few hexes from their base, and wait for encounters that involve your npc buddies and bad guys. Instant backup. Just don't try to loot any corpses until after your support is done looting first. This works particularly well with Awareness perk: sit back and snipe weakend enemies for the killing blow, or stay out of combat completely and let the two parties go at it until there are only a few barely breathing members left. If the bad guys win, they're now weak enough for you to finish off, and if the good guys win some may let you get close enough to heal them for XP + reputation. Also less survivors means more loot for you, as each friendly survivor will loot-all 1 body. I say VC is easiest because they tend to face weak enemies like robbers, slavers or ghouls in large numbers, with high payout, but nearby gecko can be very unsafe with it's TC and unguarded mine. BoS is nice and safe because they are so strong compared to their local enemies, and are close to safe and convenient junk-town and hub. They are generally low pay-out, but travel in smaller numbers, and so leave more unlooted bodies after a fight, unless sharing with caravans, junktown scouts or hub patrol, who they will not fight.
9) Consider tagging unarmed or melee. One of the less foreseeable results of the changes to mining is the inflation of ammunition prices. If metal parts are at a premium due to limited ore deposits, gunpowder is even more-so. While metal parts can be alternatively obtained from dismantling looted weaponry, the only sources of gunpowder is still limited to mined minerals. yes, small amounts of ammunition can be looted from vanquished enemies (though normally less than what you would expend bursting them), and some merchants will carry ammunition (especially low-tier, easy grinds-for-cash), but the primary source of ammunition, player crafting, has been seriously throttled. This, however, is not an issue for HtH or melee fighters. why waste precious bullets grinding mantii and pigrats when a punch to the groin will do? This is especially effective for crippler builds, as the transition from hth crippler to sniper crippler is actually pretty easy once you can afford bullets if all you are concerned with is critical chance.
10) Make friends. Don't be tempted by the path of the loner. While having its own trait may seem like tacit endorsement of that play style, this is still a multiplayer game. Yes, an extra 10% from the start is tempting, and yes, if you trust other players you will very often end up burned, bursted, or buttraped... BUT WAIT! Consider for a moment the possibility of playing with players you could actually trust. Imagine playing F1/F2 with a team of Ians and Cassidys smart enough NOT to burstmode through you to hit an enemy. FO2238 is an awesome multiplayer game not because plasma-PKing hapless bluesuits in half is awesome and technically multiplayer, but because you can respawn, gather your buddies online, and turn the griefer and all his proxy-alts into warm liquid goo. There ARE other good people playing this game... or lacking that, people with the same twisted kinks as you do with a penchant for spreading the armor-piercing love from as many smoking barrels on their side as possible. network, make buddies, bring IRL friends or buddies from other online communities into the game, and together you can specialize and take on much stronger, more experience-profitable enemies then you could as a lone jack of all trades.