Probably the most important thing you can do at any crime scene is wave your cursor over EVERY SQUARE INCH as you move around to make sure you haven't missed anything. Try just about any test on any object you get to see if it reacts. And then take it with you. Just about everything you find is a clue somehow, and if you don't have the correct object in your hands when you talk to a victim, the matching question will not appear.

Other than that, try testing, searching, and microscoping every item in the lab. A lot of times it won't be obvious that to examine an object you have to use the computer, for example. Give it a try. You don't lose points for being thorough.

CSI Crime scene Investigation Walkthrough