Don't lose your nerve. It can be easy to want to beat some hasty tracks out of a crowd or away from a bench when that red warning pops up. Hold your ground, especially if you're using Morph (absolutely indispensable for the hunted in Manhunt). There's a very good chance your pursuer may be homing in on an NPC. There's even a chance (albeit a smaller one) that he/she will kill the NPC, get frustrated, and seek out a more mobile target elsewhere.
Breaking cover when in the presence of two or more pursuers is up to individual discretion. They may very well off NPCs and just wait for their contracts to reset. In that case, I usually delay the inevitable, stun one of them, and take the blade from the second (but that's me, and I'm a loser, so here's your grain of salt).
Never, ever forget the "accuracy" of the hunters' compass. It's not an exact pinpointing device, so use that to your advantage. Use morph on a crowd and hide in a nearby bush or cart of hay (something that's already been mentioned). If you have Morph and Disguise (and they're both of higher levels), morph the crowd and then use the disguise to lure an opponent to consider everyone else.
For hunters, try not to target the player you intend to assassinate. Not only does it alert them to how many players they have following them, but you lose the specificity. The other players will appear as the directional arrows around your compass, and will widen when you get closer, flatten when you're in range, and glow when they're in sight. On many occasions using that method has helped me pick out the player in a morphed crowd.
Don't just run around. You will lose the match. I've played so many games where all my teammates tore through the streets and scrambled about the rooftops. The targets see it a mile away, and it usually leaves me (read: that one single-speed teammate) with no targets to nab. It's detrimental to your personal score to gallop everywhere. I once finished a game with fewer kills than one of my teammates, yet I had the edge on him point-wise. Six hundred points for six high profile kills vs. fifteen hundred points for two low profile kills and whatever bonuses that entailed.
Try to avoid the cheap abilities and perks. This is me speaking subjectively, but some of them break the game entirely. The Hidden Gun, Firecrackers, and Templar Vision are especially loathsome. With all that said, I can promise I do not and will not be using those.