tip a small blind, if youre playing $1/2 then tip $1, $2/5 tip $2 etc.
over $5/10 just tip the $5, or whatever singles are in the pot, a good dealer should know to leave singles in the pot.
its not about the 'big' tip, its about the consistent tip, be the guy who tips every time they win a pot, dont be the guy who says
'oh im down ill get you when im winning' -you'll never be winning.
or 'ill save up a few and get you with a big one'- youll never play another hand
or 'ill tip when i leave' -youll never leave, or if you do its only one dealer getting that tip.
dont worry about small pots, <$20 you dont need to tip those
and you dont need to tip extra in bigger pots (unless youre the douch who says ill wait for a big one, then you'd better tip so freaking big the dealer falls off his chair in shock)
Tip extra if you:
get good service, the dealer is smart and polite+efficient (has a good rack ;-), you are having a good time.
dont tip if:
the dealer is rude, untidy. not paying attention (ie watching the game on tv, he is there to work, dont reward him for not doing so).
and if any of this happens dont simply use it as an excuse to not tip, go to the floor man and say 'i am not tipping because...'
dont let your luck affect your tip, its not the dealers fault you cant get a good hand to pay off.
dont let other services affect your tip, its also not the dealers fault your drink got warm/cold.
Ive seen $100+ tips in my time, for all sorts of reasons, cute dealer, good dealer, lucky dealer, fast dealer or "I just won it from you and you're a dick so ill give it to the dealer."
Tip between 3-6% in a tournament, unless its the wsopME, then you can tip slightly less(just remember that around 1000+ staff are sharing it and you just won 10 million)
Dealers salary is irrelevant, good dealers tend to make more, unless its a country where its a flat salary, then more experienced dealers get paid higher. but if they make 200k a year then they are worth it and you should still tip well for good service, or they will stop working there and you will be stuck with the 15k a year crappy dealers who dont want to be there, deal slow, and make mistakes that cost you the pot.