Vocabulary lists are ok but slow, learning phrases and sentences is much better. This does not mean you should not learn vocab lists, it may suit you at times.
Unless you have to or need to then stay away from colloquials… all of them and learn MSA or Classical first, its easier that way, although often it may be unavoidable.
Listen to audios of Arabic speakers in the target area that you wish to learn. So if you want to learn Modern Arabic listen to the news or documentaries. If you want to learn Classical Arabic listen to the Quran, talks and some debates.
Every now and again practice your spoken Arabic with the little you know, until you get regular conversation and used to talking.
Use all the language skills not just reading.
You do not have to study complex concepts all the time mix it up sometimes by being exposed to a variety of simpler material, in fusha Arabic.
Learning a little daily is better than cramming at the last minute or trying to do too much in a short space of time.
Revise, review, repeat. Whenever possible try to go back over material you might have already covered no matter how long ago it was.
If you are having group lessons the smaller the group the better the results. Likewise the larger the group the more distraction or potential for time to be wasted. Try to learn with people who are motivated and consistent.
Self study may not work for most people but if you have a 1 to 1 with a tutor this may assist you better than going it alone or being amongst groups.
There is no big secret to learning it is all about being consistent. If you accept that there will be challenges and that some concepts may take time to understand you are more likely to last longer on your learning path. If you have good reasons for learning Arabic you will have more enjoyable moments. You will likely encounter a range of tutors, resources and books, some better than others.
Despite any reservations that you may have about a particular resource there may also be a positive aspect to it that adds to the overall learning experience.