I have no luck with yeast

Are you using yeast in a little foil packet strip? If so, check the date printed on the end. Yeast doesn't live forever. It may have been expired. So buy some new yeast and try again.

Also, you can kill yeast with too-hot water. Yeast likes the same range of temps as humans. The thermal death point of yeast is relatively low: 120-130 degrees F. So boiling water or very very hot tap water used to "bloom" or "proof" the yeast will kill it.

It depends on the recipe. If you're using active dry yeast in a recipe that's fairly dry, you can combine the yeast with some lukewarm water for a minute or two before adding the liquid to the recipe. In a wetter mixture (like, say, waffle batter), you don't need to proof the yeast (unless it is ancient and you want to make sure it is still alive before proceeding).

I prefer instant yeast to active dry yeast. It's sold as instant or as bread machine yeast. A more concentrated form, it needs no proofing and can be added directly to a mixture.