Once of the simplest things to remember is to go slow. Don't be in a hurry to get into LOS and shoot, because being in LOS means "they" might shoot first and more, which is bad.
Within the confines of the time limit you're under, recon, recon, recon. The longer a scout watches, the more they might see. The more you see, the easier it is to figure out where to apply your firepower or support when you do open up and take a short term objective successfully before seeing what the next manageable thing is.