Strategy:
KitingEluding your enemy and giving distance to the fight. You want to always keep your enemy as far away as possible but you want to also be able to attack him at the same time. The technique is to damage your enemy while falling back, you obviously can not do this with certain builds but as long as you do not need to be stationary you should always be moving. Avoiding damage as much as possible is as easy as turning around, sprinting and then turning back around to shoot continuing to move backwards from your enemy. Be conscious of what is around you and always be looking at your radar to see where your team mates are. Normally if you are in the front line of your team its a bad thing unless you are quite a few levels higher then the mobs you are fighting.
EscapeKnowing when to use this skill is very important to your survival on the battlefield. If you are surrounded or have multiple enemies attacking at you from aerial or a distance best choice is to use Escape and gain the advantage. You can gain this advantage by either healing or just by giving yourself a little more ground to shoot that pesky monster. Another great reason why Escape is nice is, depending on how high your escape level is, you can get a good portion of your shields back while you’re in the protection of Escape. Tie this skill to a trigger button (reaction key) and be ready to use it!
TargetingThere are plenty of ways to target monsters but some of those monsters are just harder to hit then others. First example would be the mini monsters that get to close. If you play in 3rd person you will not be able to hit the ones closest to your body but you can solve this by easily scrolling into 1st person.
Second example, are those annoying Orbiles that seem to have no hit box at all. You can solve this a few ways, first way is if you have ricochet proc’d you simply shoot at the ground and the bullets will bounce up and hit him ignoring any hit box that monster has. Second way you can do this is by changing your height advantage, if there are open buildings around use them and get above the monster, if you can’t seem to hit the target drop down into a stance and that lower elevation may be able to hit the monster.
Third example the new dragon-like flying creatures. They have a very small hit box which is located in the very middle of there body. I have found that if you are targeted straight ahead of them or behind them it is easiest to hit that target.
Fourth example is the most fun, when you have Ricochet proc’d and there are no bad guys in site…. Well that doesn’t matter keep firing in front of you anyways. When Ricochet is up it gives you about 3 times the range due to a nice little bug. Firing ahead of you will clear the path of monsters you haven’t even seen including enemies around corners or behind objects.
Fifth example, When using a sniper rifle you have to lead your target like you would in hunting. The bullet does take a while to hit the target so make sure you keep an eye on the enemy and his movements and shoot a little in front of where he is moving and you will have your money shot.
LevelingThis used to be a much easier task with solo leveling groups but since the 1.0 patch it has become just a tiny bit slower. The best part about the marksman is that they can beat up the big bad boys at 8 levels higher then themselves and not feel any pain. I have found that even though kicking the crap out of level 8+ mobs is fun, it doesn't do the job for leveling. You want to pick those level 3-4+ mobs and farm the crap out of them, any hell rift you find and any bosses you find just keep kicking their ass because it will reward you with the most XP. Try not to stay in the same level range as your current level. It's much easier to kill things but far less XP then you are looking for.
Another thing to be doing is completing all of the side quests you get. Although these quests seem very lame they are usually on your way through an area you already need to be going for your main quest, so why not take a few extra steps and earn some XP and maybe even a couple Attribute Points (you'll have to do those quests anyways so why not get it done now). Quests are going to help you out a lot with XP and not only that will give you certain armor that you would not have found otherwise. Its a drag to do the same quests all over again with a new 'toon' but believe me it is very much worth it.
Disclaimer, this guide was made by a guild member who does not use d2jsp. All I did was edit parts and make it easier to understand.