Most folks immediately understand the value of implants to speed skill learning. Far fewer seem to have a handle on the value of hardwiring.
Think of hardwiring as "mind-rigs".
The hardwire modules impact a specific attribute of the ship that you are currently flying in the same manner as rigs installed on that ship. If you need more cap, you can install a Semiconductor Memory cell rig on a particular ship. Or you could plug in a Squire CC series hardwiring to give you additional cap on every ship that you fly!
Like rigs, hardwirings are lost if they are removed, so you do need to think about what you plug into the clone head that you are inhabiting.
If you have multiple clones (you _do_ have multiple clones, right?), this gives you the opportunity to design a set of harwires to compliment your personal style & ship choices.
Like most of Eve, there is no single _right_ answer. There are simply choices.
Here is a spreadsheet to help you examine the various hardwirings and their impacts. THe organization will be obvious when you look at it.
I've also included a few suggestions for typical harwire sets for those kinds of characters that I am most familiar with (Caldari railgunners who mine), but I'm not suggesting that these are optimal. You should use them as a starting point for your own exploration of the benefits and costs of using hardwirings.
Oh, and the disclaimer:
Use at your own risk. No warranties are provided, either expressed or implied. Your mileage may vary. Side effects are generally mild and include bloodshoot eyes, flat wallets and bruised foreheads from contact with desktop. In some instances, may result in a significant improvement in the capabilites of the character in question, leading to combat losses by those shooting at you. Do not use in connection with the ingestion of alcohol, perscription drugs or other mind altering substances, regardless of their legality. Do not operate heavy machinery for 12 hours after first exampination. If you experience epeen tumessence for more than 4 hours after plugging in your first hardwire, please consult a physician.