Should you lube your bearings in any way to help them out? Is WD-40 a good idea?
WD-40 is a bad idea for healthy bearings. Although WD-40 displaces water (good) it also dissolves grease (bad) so you should keep it away from bearings that you don’t plan to carefully pack with grease afterwards. WD-40 acts as a lubricant for a short period of time after which it evaporates.
Would regular axle grease that you find in auto parts stores be ok for bearingsand axles, or should I use something else? 
Yes, if the bearings aren’t sealed they’re easy to pack and axle grease is fine. The seals can be popped off of them and popped back on pretty easily if they are sealed. Depending on the bearing, it might be so cheap that it would be better to just buy new ones. I can’t think of why you would want to grease an axle other than to put a crank on.
How would you go about popping off the seals ???
Most people use a club:
Personally, I prefer using a handgun, but that’s just because I like to take every opportunity to pop a cap.
A typical pick that you find at the hardware store works just fine, just be careful not to damage the seal.
The attached pics (tee hee) are presented at the McMaster-Carr website; there are a bunch.
Why the heck would you want to open sealed bearings? Aren’t they sealed for a reason? Do they actually need maintinence, cleaning and repacking often, or at all? 
Well, if your uni landed in salt or even fresh water, or you ended up in a lot of sand, it might pay to remove the seals, wash out the bearing with degreaser, blow out the bearing well, repack it (squirt in more bearing grease), and replace the seals. If you rotate the bearing, and it has a gritty feel, then it’s possible that the above procedure will help smooth out the bearing once again. If, of course, a ball is broken, then repacking will not help and you need to replace the bearing.
The seals on the bearings we use are more like impediments, not actual watertight compartments. They kinda keep the dust out, and the grease in. This keeps the cost of the bearings way down.
Another reason to repack a bearing set is to use a different grease for extreme environmental conditions, such as extreme cold.
There may be exceptions to the above procedure, so if you have specific questions, you are welcome to email me at LiveWire Unicycles.
The SKF website has many good pages on bearing seals if you are keen on the topic.
Alms? Alms? Alms for the poor?
…er…
Links? Links? Links for the lazy?
My bearings are lubricated with smooth, slippery mud and maintained with the power of ignorance. I find that the resistance they add even when a bit gritty is next to nothing compared to the tyre on the road and my awesome speed against the wind.
When they eventually become so stiff that they won’t turn when left in the garage for a few days, they just get replaced, none of this faffing around with trying to unseal the seals…
Phil
I don’t think it’s funny. 
I hate people who hurte animals for no reason or for there fur and it’s nothing to make jokes of!
I was hoping for a link to the articles U-Turn had mentioned… I found the home page but I found the site/search hard to navigate…
Just click on Products and look around, there is lots of material to look at. The articles discussing seals, sealing technology, lubricants, etc etc etc, are spread all over the place. There’s a small entry fee for this information – a little time to get to know the place. It’s not like a textbook where pedagogical techniques are used to carefully time the material.