If you still having some problems with this rather troublesome aspect of English grammar then I would strongly recommend going here:
and just working your way through the tutorial and the exercises. For those of you with access, there is a pdf version of the tutorials and all the lists on my Dropbox, along with the first two exercises from each tutorial. But you would do better to do the exercises online and get instant feedback.
With regards to the difference between the constructions:
I like skiing and I like to ski
you may find the following helpful:
“In I like skiing the important bit is the like. You’re talking about something you enjoy, and not saying much about the skiing. You might like doing it, watching it on TV, or you might just like the idea of it, because of all the clothing and those fancy goggles you wear.
In I like to ski you’re saying something about what you enjoy, but you’re also saying something about skiing, ie that it’s an activity that you actually do. I like to ski is not appropriate if you just watch it on TV.
In other words:
I like skiing = I like skiing
I like to ski = I like skiing + I ski”