tutorials. Best way, it worked for me and Ive been using ps for over a year and im only 17. Go to web layouts and start following what they say (VIDEO TUTORIALS ARE BETTER ).
Whats your interests? Try and find some sites that attract your attention and look what works well and try to re-create it within your designing program.
Its best not to just stop at web layouts, learn other tutorials such as 3d logo's gradients and icons. As eventually you will pick up the ability to apply it with-in your work without referring to anything.
As it will then come naturally.