Without the Hide in Plain Sight ability, you need stuff to hide around like bushes, rooftops, shrubbery, a series of counters in a dark general store, rocks in a canyon, that sort of thing.
Sniping requires you to be at least 10ft away from the target, you may make a single ranged attack as a standard action and then can attempt a stealth check to remain hidden at -20. You can still take a move action to move around while sniping, but moving while hidden also imposes a stealth penalty. The expert Sniper perk and the Signature Skill (Stealth) unlock at 5 ranks both take -10 off the penalty for sniping. This can allow you to snipe more easily. While sniping your opponent will be denied his dexterity to AC, however you cannot apply sneak attack beyond 30ft without Sniper's Goggles (magic item) or a class ability.
All of these are opposed checks, your stealth roll (at various penalties) vs the opponent's perception check. If the opponent rolls high enough to see you, they've spotted you and you'll need to break line of sight to hide again.
Basically, every round you shoot the guy once and he gets a perception check. You make a stealth roll. If he rolls higher than you, ever, he sees you and knows where you are unless you can find a way to hide again. Usually this will require either breaking line of sight or making a successful bluff roll against their sense motive to either create a distraction or otherwise successfully juke and hide again.
+1 to the above but don't forget about the Perception penalties for being far away, it can effectively reduce the chance of being spotted, so try and put some distance between you and your enemies.
Probably gives you soft-cover (20% miss chance if they can see you) since you are close enough to the edge to be peeking out and firing. No other changes to the above rules, you'd still be making stealth checks. They'd still be making perception checks.
Probably gives you soft-cover (20% miss chance if they can see you) since you are close enough to the edge to be peeking out and firing. No other changes to the above rules, you'd still be making stealth checks. They'd still be making perception checks.
You're thinking of concealment. Cover is a +4 to AC. I believe if you're behind a corner and you have clear line of sight (one intersection of the square you're in meets two intersection of your target's square), they also have line of sight to you, otherwise both parties have cover.