Rip is good, but a little crazy at times. If you go to youtube, type in the type of of RDA you have, or are thinking of buying, or just RDA RTA to get a list of videos. You can type in coil rebuilding, etc. It's not all that hard, but you'll wish you had an extra hand. Some are trickier to build on than others.
Basically you need
Kanthal I was told to start at 30 gauge.
something to wrap it around, (screw driver, drill bit etc) or a coil jig
fingernail clippers or scissors
something for wick, most are using organic cotton, cellulose cotton (aka rayon) or Koh Gen Doh (KGD Cotton)
coil toy or other coil calculator
Coil Toy - Online calculator for e-cigarette resistance coil building
screwdriver or tool to loosen screws on device
Maybe a lighter or butane torch to torch the kanthal, but not everyone does this.
Ohm meter (or use built in one on a mod)
Not sure if I left anything out. Sounds a lot more complicated than it is. Youtube is definitely your friend. Definitely start with a regulated mod, not a mech mod til you get to know what you're doing. You can really mess up big time with a mech mod if you don't know a lot about battery safety.