I'll attempt an answer, since I've been sort of playing with this recently both on beige boxes and on B&Ws, although I've been doing processor swaps more so than overclocking.
As you might have gathered from your reading, the processor speed is set as some multiple of the bus speed.
On the beige G3s, the bus speed is 66mhz, and I have been advised not to change this.
So, this leaves playing with the multiplier.
At 233mhz, your multiplier is going to be set at 3.5x. Most sources I've read advise-with the same CPU-not going any more than .5x higher than the stock speed, although you can occasionally push this to 1x higher. This means that you could set the multiplier to 4x safely, and end up with a 266mhz system, or possibly go to 4.5x and get ~300mhz. You will have to experiment and see if it's stable with either of these.
One of my beige G3s is currently running at 400mhz(6x), although I'm using a 400mhz G3 out of a B&W.
As you've probably also encountered, this is done by changing jumpers on the logic board. There is a small, one piece jumper block under a "warranty void if removed" sticker on the logic board. On B&Ws, this is right next to the CPU, while on beiges it's over next to the PCI slots. These blocks are color coded and have all the correct jumper settings for the CPU frequency that the computer shipped with.
You need to remove the block, and then use individual jumpers to set things as you want to. There are 9 pairs of jumpers on the beige logic board. These are numbered 1 through 9. If have the front of the computer(optical drive, etc) facing you, 1 is the closest to you, and 9 the furthest away.
Jumpers 5-9
should not be changed from their stock configuration. This means that you should have jumpers on #5,6,7, and no jumpers on 8 and 9.
To up your processor to 266 mhz, you need to jumper #2 and #4. To go to 300mhz, you need to jumper on #1.
I should also add that you need 2mm "micro" jumpers and not the standard 2.5mm hard drive jumpers. I bought 100 of them here
http://www.ebay.com/itm/350557475053?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT
(For the mods-no connection with seller other than a happy customer).
The last thing is that by increasing the speed, you will also end up with a hotter running CPU. If you have the G3 "outrigger"(desktop) there's really not a good way to get a fan on the CPU. I'm still experimenting with good ways to get airflow over it. If you are fortunate enough to have a desktop, you should be able to stick a thin fan directly on top of the heatsink(as I did with my B&W G4 upgrade).
Finally, have fun! I don't know a whole lot, but this is something that I'm educating myself about and "learning while doing."
