The alerts don't happen as often. Running by guards won't get them to chase you like in the first. And if they're watching you, you can just keep walking away and they'll give up. You can decrease your notoriety in 3 ways: removing wanted posters, bribing heralds, or killing a certain enemy (they only appear on your map when your notoriety is 75%). What also helps is you can hire mercenaries or thieves to help fight large groups of enemies. And you can often do a quick kill if you're behind a guard that's fighting a merc/thief. You also get smokebombs later on so you can use one and run away.2)when you got spotted there were way to few places to hide in order to stop the "alert". about 8/10 times I got spotted I ended up in a giant fight, running, they'd catch up, and like 9 guys would encircle me and kill me.
Needless to say I think I got to block 5 and sold it without finishing it.