If you stay in one spot too long, you will definitely wear out your welcome. You should develop an automatic clock in your head that starts ticking once you reach a spot. Once the alarm goes off, you've been there too long, time to move. A good tactic in gaming is to know a few key hiding spots, where the opponents are not likely to look, and you can let them go past you. People usually do not look backwards, they move forwards. A dead end alley works well, or a small ditch where you are out of sight. Crawl from one small ditch to another, and they won't see you. Then stand up and use cover to move to a new spot. If you hide in an alleyway, wait for a minute or so, then listen for a lull, and come back out ready to go. Small breaks give you a chance to make a new plan, and it keeps you from getting targeted.
Hiding can also be effective for ambushing. You find a spot where you can just barely catch a glimpse of someone as they go past, and then tail them. Make sure to look that there is not a second person following your target.
Camping is usually hiding in spots with a high tactical value. Finding a spot that conceals you, while you have a good view of a flag or target. The best way to find the key spots is to go into a server with a few people, and try different spots out. Try the spots from both angles, as an attacker, and as a hiding spot. Find the areas that work best, and find multiple areas close to that spot, so you can keep them guessing. If you can't get into a server, you can try hiding in a game server, and see how close people get to you before they see you. If they walk right on top of you, then it's a good spot.