Id buy in for what you feel comfortably playing, if you cant afford to lose x amount of money, than buy in short or move down levels. From a strategic point of view, you should want to have as many chips on the table as you can have. But if the table is super deep and you can buy in low, than its also strategic to do so. I play $1/2 live, sometimes i buy in for $100 sometime $500, it depends how many chips are on the table, how my opp rates, etc. If everyone has $1000, i always buy $100, as a double up will be easy, sometimes youll double up without a call($20 raise and 4 calls, u push) If everyone has 200 and under, except this lady whos got lucky on the river three times with money in on the turn, and has $700, im buying $500(70% of opp stack) Both examples are real, i have doubled up without a call preflop, and i did buy in and double tru the lady who reraised my turn bet with two pair vs my turned strait.(side note the $500, was a $200 buy in, a $100 add on, $100 add on, $100 add on, the lady did look at me weird, as i did this after each of her drawouts, but didnt keep her from getting it in with me on the turn) turn action was bet 20, she rereaised 100, i reraised 350 more, she did wait about 30 seconds before calling, for anyone who cares.