re: Poker & topping up stack in live cash game
Funny how things work differently in different places. Where I play the dealer and the rest of the table would look at you like you had two heads, or were some kind of cheat, if you suddenly reached into your pocket to get more chips to put in play once you got low.
Standard where I play is to just put your money on the table, next to your remaining chips, when you're not involved in a hand. The dealer will change them for chips before dealing the next hand or, alternatively announce "money plays" before he deals if he just doesn't feel like doing it right then.
As for amounts, in a 1/2 game people often top-off every $40 or so. You could do it at $20 increments, but that seems a little extreme.