Ahh, paintball. What a wonderful pasttime. Prepare for a LONG post. Should be VERY informative though.
Reading previous posts, it sounds like a lot of folk have played with some real jerks on the field. But, like any sport, you're going to run into jerks, just like you'll run into really cool people to play with. Just try not to get discouraged if you do run into the jerks on your first time out.
Now, as for tactics and strategies, it really depends on what type of paintball you'll be playing. If you're playing supair (The big inflatable balloons on the field) then your tactics will change from if you're playing recball in a wooded or more natural environment.
I never really got into supair, so I'll leave those strats to those that have played it. For recball though, there's a lot that I can share.
First off, remember to always listen to the refs. And more importantly, don't SHOOT the refs. As much fun as this may be, most will frown upon this behavior and kick you off the field if it happens too much or intentionally.
Use cover as much as possible. You're an easy target when out in the open, even if you're moving. It's real easy to correct your shots as you're shooting at someone, since each shot works like a tracer, since you can see exactly where your paint is going in the air.
When you're behind cover, don't keep popping your head out of cover in the same place. Always pick a different place to pop out and shoot from. Otherwise, your opponents will get a bead on your, and just aim and wait for you to stick your head out again.
Additionally, when you're behind cover, be mindful of all body parts, and make sure they aren't sticking out from behind cover. I don't know how many people I've eliminated simply because part of a foot was sticking out, or maybe a refill pod was poking out. Conversely, watch for your opponents to make the same mistake. Even veterans do it from time to time.
When you come under fire while behind cover, listen and watch for where the paint is hitting. One of my favorite tactics against a newbie would be to trap him behind cover, and then shoot the cover incessently. While some might say it's a waste of paint, it has an effect of demoralizing the rookie player to a point where they stay tucked in their bunker, never popping out to return fire. This would allow me the perfect time to hop out of my cover, rush their bunker, go around, and shoot them while they're still hiding behind said cover. (That move is known as 'bunkering' someone. Rush them and take them out while they're still in their bunker.) If you hear the paint hitting your cover a lot, then either they're trying to scare you into staying behind cover, or they're just really bad shots. Either way, it means they aren't shooting around the edges of the cover where you'll be popping out to shoot them. It's usually safe for a quick snap shot in their direction to force THEM back into cover.
Depending on how much paint you can afford for the day (as well as what type of marker you'll be using) will really determine how you want to play, as well. If you can afford more paint, feel free to use spray and pray tactics. This will usually keep more novice players hiding behind their bunkers and not shooting at you, allowing your team to move up and clear the bunker. But, it gets real expensive real quick.
Making more selective shots is a lot more difficult then it sounds, especially when using rental equipment. This includes sniping (Extremely fun if you have the gear. Not so much fun if you don't.). The rental gear is usually poorly maintained, not very accurate, and just not as reliable.
If you're using a pump, however, sniping is pretty much the only way to go. Pumps are extremely accurate, and are great for conserving ammo. But when your up against a full auto, it's a bit more difficult in a 1v1.
Contrary to what some people have said, blind shooting is NOT a good tactic. Not only do you risk hitting your own guys, it's also an extremely unsafe practice, and most fields don't allow it. If a ref catches you, you'll probably only recieve a warning. Enough violations, and you run the risk of getting booted from the field.
Never EVER call yourself out, unless you know 100% for certain there is paint marking you, or you're getting hit repeatedly from the same source. I've had numerous paintballs hit me but fail to break. In most situations, it's best to wait for a ref to call you out. If you're under heavy fire, and have a lot of near misses, the opponent may call for a paint check, where the ref will stand you up (You can't be hit during this time) and he'll give you a looky-loo for paint. Feel free to do the same to your opponent if you think you've landed shots on him as well.
If you DO call yourself out, or even the ref calls you out, make sure you immediately raise your marker above your head (Just be mindful to keep it level. It sucks when you raise your maker over your head, and a loose hopper lid pops open, spilling out all your remaining paint.). Keep your marker over your head until your off the field. This is the universal sign for "I'm out. Please don't shoot me anymore."
Running right along those lines, be mindful of something known as the Dead Man's Walk. While many fields frown upon this maneuvor (And some outright forbid it), I've still seen (and performed) it used many times to GREAT success. A Dead Man's Walk, is when you 'pretend' to be out, and just start walking towards the sidelines, making sure to take a path that takes you straight through enemy territory. You just walk out from your cover, and start walking. No shooting, no running, no dodging. Once behind your opponents, you shoot them in the back. Of course, this runs the risk of you being an easy kill, as any veteran player will immediately shoot you, unless you've officially called yourself out (or have your marker raised above your head.)
Another great tactic is to try and get behind enemy lines, turn around, and then act like you're on their team. Sure, your team might take a few pot shots at you, but on the flip side, you've got REAL easy targets sitting side by side with you. Just make sure your armband is on the opposite side of where they are, cause if they see that, it's game over. Often times, players will only pay attention to which direction people are facing and shooting. So, if you're shooting in the same direction they're shooting, then they'll think you must be on their team, and drop their guard, allowing for easy eliminations. I've had this work so well for me, I was able to get extra paint, when I was running low, from the enemy team, because they thought I was on their side. Was VERY poetic when I shot the guy with his own paint. *Evil grin*
Well, there's plenty more for tactics and strategy, but I think that's MORE then enough for you now. Provided you even read through it all. I know most folk don't like reading these long winded posts, but, I had a lot of info to share, and well... You asked for it.
Good luck!
And feel free to ask me more questions if you have them. I'd be happy to answer.