Taking the initiative
They key to successful 6 handed cash game play, is to always play in as profitable and efficient manner as possible. This means picking up small pots where possible, very rarely calling raises, never open limping and being aggressive preflop in position. The aim is to be like a machine, on average, being the one doing the raising preflop and the one who is constantly betting rather than reacting to someone else. Calling raises, out of position especially, is the sign of someone who will not do well at 6 max. The preflop raiser has the initiative and will win the majority of the time. To call a raise preflop your hand should either be much stronger on average than your opponents (ie AK or a pair), your opponent awful, or the preflop raise very small.

Playing broadway cards
The most profitable way to play unpaired, unsuited broadway cards (AJo, AQo, KQo etc.) against normal opposition is to either reraise with them or fold. The nature of these cards is to make your hand very obvious should you hit it, so its more profitable to semi bluff with them. The converse is true with mid pairs, their strength is concealed. Even a tight opponent can lose a lot of chips if he raises with AT, hits a ten and you have jacks.

 When you reraise with them you should bet about 2/3 of the pot should you miss; representing an overpair. Be more inclined to reraise a late position raiser than someone raising under the gun. To make this profitable you need to be very disciplined when your bet is called on the flop. The other player has called a reraise preflop, and then a bet on the flop. In theory he should always be able to beat aces or kings. Only continue if you have a specific read that he is weak, there is something you can represent, or you have a strong hand yourself. Finally it should be obvious, but don't attempt this against very loose opposition.