Mastering Your Playstyle

"From our observations, we have noticed two main game-play styles: Players who are mastering the social stealth aspects and the players mastering the free-running. In both styles, the fight has to be mastered to achieve high scores."
-Stephane Baudet, Multiplayer Creative Director, Ubisoft

First things first, you must decide which playstyle you are. You can find this out by thinking about what abilities you choose, the way you traverse the map, and skill set.

Mastering Social Stealth

This will stem from patience, and for that there is no real way to practice it. But what you can do is get abilities that will help you achieve stealth. Morph and disguise, mainly. If you haven't yet, I'd recommend you read the "Choosing Your Abilities" article. Focus on blending in when you are close, as the person your hunting may know what your persona is. This is where disguise comes in. When you are nearing your target, slip into the disguise, then approach and kill your target with ease. Morph is helpful for hiding in a crowd. If you can avoid going high profile you will receive bonus points. But since freerunning is more efficient for map traversal, you will receive said points much less often.

Mastering Freerunning

This will come from single player skill. I'd recommending going over to the story mode before you play multiplayer, read the Parkour Tutorial article, or do the virtual training "Freerunning Tutorial".