Nothing is written in stone, music is expression, not mathematics, so feel free to disagree with my point of view. Rule 2 - Use a firm pick. If your pick is too soft you won't have a great tonal range. Rule 3 - Play every day. If you don't want to 'practise', sit down and play for fun.
Enjoyment is a big part of progress.
No matter what your main style is, I guarantee one will compliment the other. Rule 5 - Loosen up. Before you play, loosen your mind and your hands. There is nothing worse than 'stiff' guitar playing.