Lead vocal tracks almost always benefit from at least some compression. See my tutorial on using Reaper's ReaComp compressor plugin to see a video of how to apply compression to a vocal track here: Vocal Compression Using Reaper’s ReaComp Effect Plugin. In that tutorial I applied mild compression and I only did it once. That's pretty much the norm. But you can use more compression if the vocal track is very weak, tentative, and/or particularly uneven (volume-wise).
But how do you avoid the nasty side effects of over-compression, which include things like hyped sibilance, pumping or just very flat-sounding audio? One way is to use something called serial compression. What that means is that you apply subtle compression to the vocal track, but you do it multiple times. That way you can get the desired effect of more-than-usual compression without ass the side-effects.
Bjorgvin talks about what that is and how to use it in his article here: