I also used to not really know what I was doing, but after a lot of experimenting and reading up on the topic, I've come to know how to overclock fairly well.
First of all, you need to know that you need to overclock your processor without overclocking the RAM (this deals with the ratios). If you notice, when you go to change setting of your RAM, you'll have a max MHZ (I think that is what it says). Here is the ratios (RAM:CPU-FSB)
200 = 1:1
166 = 5:6
133 = 2:3
100 = 1:2
Another thing is that you want to make sure you don't overdo it on the HT frequency. You have some choices here (5, 4, 3.5, 3, 2.5, 2, 1.5, 1) I think those are the choices. What your computer does is take the FSB speed and multiply it by the number selected here. You want to make sure you total does not go over 1000. For example, if you have a FSB speed of 250, you will want at a max 4, but probably 3.5 to be safe. You want to make sure that you DO NOT exceed 1000.
Finally, to overclock you'll either want to change your multiplier (which I don't think you can go any higher than 9 with the AMD Athlon 64 3000+) or change the FSB speed. When you up the FSB, REMEMBER: you also have to make sure the RAM:CPU-FSB ratio is not too high, or you may get just a black screen, AND make sure your HT frequency does not exceed the total of 1000 (multiplier x FSB).
The only other thing to know is that you'll have to increase your voltage along the way...I mostly have just experimented with this.
AMD Athlon 64 3000+ socket 939 @ 2.3 GHz
MSI K8N Neo2 Platinum motherboard
EVGA GeForce 6800 GT
2 GB DDR 400 (PC 3200) (2 x 1 GB sticks) (Dual Channel)
DVD player and seperate DVD RW drive
80 GB Western Digital Hard Drive
500 watt power supply
Sound Blaster Audigy
Logitech 5.1 surround sound speakers
SAMSUNG SyncMaster 710T LCD monitor
Aspire X Navigator Case