There are some forum posts players made about some common newbie mistakes and how to avoid them. I don't have the links saved because I'm already well versed with them but you can ask the chatbox on the homepage for them. For starter ask for the link to the Yoko and Cindy tip page KuriKurisataru made (more like a complaint page lololol
Anyway, a quick tip: If you're playing Desperate Times, avoid making the item spots on the ground disappear by putting them into an empty inventory slot. Always replace them with another item you have. You need the spots for the siege and others will be very miffed if more than one spot disappear (less if you take away a spot right at the front gate cuz the team spawns there). This also applies to Wild Things and the items at the plaza before the boss fight. You need them so you can haul the medals back and forth to the racoon statue.
Also on Desperate Times: If theres two stacks of Handgun Ammo at the front of the police station, don't combine them. There's a reason they were separated.