As far as the amount of the overclock, that depends entirely on your hardware and ability to work with it within its limits. On to cooling. To answer this question, we need to know what kind of power supply you have running in that thing? Multiple fans means more power, which means less voltage to go to your hardware for the overclock. You need to find a nice medium, this is why most good aftermarket fans will tell you their voltage requirements when you look at them before you order. Three fans is overkill. A good fan (a low level, good fan) is going to cost about 15.00. Lets math, shall we?
v'e got a slot 1 type Celeron 266 processor (not much, i know), and an ASUS P3B-F motherboard.
the motherboard as far as i know, supports up to 150 FBS and goes up to an 8x multiplier.
What i'm wondering is how much would i be able to overclock that processor, and still keep it moderatly safe (decent temperature, decent lifespan, etc), and what cooling methods could i use?...i was thinking prehaps 3 fans on the processor (2 on the heat sync and one on the back)?