At the moment I’m reading Bill Handley’s Fast Easy Way to Learn a Language, which, as the title suggests, has lots of useful tips about learning languages.
One suggestion I particularly like is to compile a list of words and phrases you want to say and think will be useful to you, then to get translations of them in the language(s) you’re learning, and audio recordings as well, if possible. This will give you a personalised phrasebook that you can continue to expand and improve as you learn more of the language.
I suppose the phrases section on Omniglot could be thought of as my personalised phrasebooks for various languages. It’s something that started as a small collection of ‘useful’ phrases and has grown quite a bit since. I’ve just added a new page with Italian phrases, by the way.
Another good suggestion is that you use several textbooks: one textbook might not explain all the grammar or pronunciation very well, while another one might explain some of it more clearly. Each textbook will also contain different vocabulary and cultural information.