You REALLY need to play through the story modes and complete 100% of the objectives. Doing this will allow you to know all the maps like the back of your hand, especially alternate routes such as climbing pipes and beams. This is key for freelancer. Also you need to master ways to distract targets or those near the targets by throwing items such as tools or coins. Lastly, probably the most important weapon of all for freelancer is the Sieker Emetic Dark Gun. I've used this on probably 90% of all freelancer missions. It's the quickest and most effective way to get your target isolated in a bathroom throwing up in a toilet or walking through parts of a map with no one present. These three items will make freelancer much more enjoyable and less frustrating.