I will mention only the two most important tips which helped me effectively learn two languages:
1. Listen and speak before reading: If the textbook comes with recording for example on a CD, listen attentively and repeat after each line or phrase as best as you can until there is no longer stress. Only then, open the book.
2. Don’t stress about remembering words: When encountering an unknown word, look it up, make a mental note of it, then move on. It is neither necessary to stress about not being able to remember a word after you have seen it seven or eight times nor painfully cram vocabulary.
This site offers many good tips.