How do you know when your spokes need to be tightened and is it safe to tighten them yourself if you don’t know what you are doing (ie. could I destroy my wheel by doing so)
Assuming your wheel was built correctly to begin with, you shouldn’t have to tighten your spokes unless the wheel becomes out of true.
If this happens, then identify the area of the wheel which is out of true (spin it in the frame, attach pens or something to the frame with zip ties to help identify it), and increase/decrease the tension of the spokes on either side in order to bring in back into true. Only adjust the tension in each spoke by a small amount (max of about 1/2 a turn).
There’s additional truing for if your wheel isn’t circular, or if the rim isn’t centred correctly, but it’s fairly obvious what to do to correct it, and probably won’t be necessary. Work with small adjustments. It may be helpful to keep a loose spoke and nipple next to you to remind yourself which way increases the tension in the spoke.
Re: ? about spokes
It’s best to have your wheel worked on by a trusted professional unless you are willing to take the time to understand what is going on. Simply twisting a couple of spokes may make your rim wobble less, but actually weaken the wheel overall. When you ride on the wheel, if you “tweak” improperly the wheel may settle into a new, just-as-poor tensioning. A well-built wheel is a carefully orchestrated application of principles and techniques. There are good printed references out there that can help you do the job properly if you want to do it yourself.