The best mapping method is one which you are comfortable with and gives the best final results. I am being cpt. obvious here, however that's how it is.
Now, to find that, you require experience and knowledge. What people usually tend to ignore are combos, they are actually very important, because if comboing is done right, you can automatically see "sections" and how they should probably look like. This makes fitting patterns much easier to make and greatly reduces the amount of spacing errors you may create (usually if you know how to analyze the song properly, you most likely won't make a single spacing error).
Another big thing is the beat logic, and that is you might want to create rhythms that are in the music and are kinda obvious. If you just place random beats thinking it sounds great, but doesn't go along with the song, that's pretty bad and unintuitive and results in a bad map usually (by some people's standards).
And the biggest thing of them all if you ask me is the song analysis. You listen to the song and it's composition and you can distinguish specific rhythms in it. This is very important because it allows planning and when you are able to plan something there is almost no chance that you will create something "wrong" (as in errors, really unintuitive beats or overmapping based on the person's feelings which may clash with another person's feelings). This also tells you how dynamic the song actually is and you can reflect that through your map be it via hitsounds or slider velocity (spacing). It also tells you which are more fitting objects for your map as well, instead of just having a random amount of sliders and circles bunched up together, the planning allows you know exactly when you want a slider or a circle (a holding vocal usually feels much better as a slider for example, while sudden beats feel much better as circles).
Those 3 are most important if you ask me. If you're inexperienced you might find it hard to incorporate all this, however everything is hard at first and be prepared to fail on your first attempts, a lot.