How to Make Infinite Lava and Water
Currently, the most reliable source for lava is at spawn. Since the server protects the area, it is 100% failproof. The other methods are extremely buggy as of the latest update.
Making infinite water is a much simpler process. Just make a 3x1x1 ditch. Put a disposable block in the middle. Fill either side with water. Destroy middle block. Instant infinite still water. Fill your bucket from the middle block.
Materials you will need
Buckets. You'll need at least two for the water. Having more on hand to load up on your infinite supplies is always a good idea. Making buckets requires three iron bars and they do not stack. See the Minepedia Crafting Page for the simple formula.
Easily destroyable blocks. Such as Sand, dirt, gravel.