Before you even start looking at different tools and strategies, it's important to think about... you. Why are you wanting to learn French? What do you hope to achieve? And how soon?
Doing this now can also help cut down on some of the analysis paralysis you might feel around choosing tools for learning French. You'll start to gravitate towards some tools, while being able to easily cross others off the list.
So, first things first...
What would be the ideal end-point for your formal French study? How well do you need to be able to speak and understand French?
Obviously, if you're just looking for some basic phrases to use while on vacation, then you can probably skip the nitty gritty details of how the grammar works and focus instead on a course that teaches you practical phrases and basics.
But if you want to be able to interact with people in a more natural way, then you'll need to stop memorising phrases, and pick up a good grammar course. This will usually take you to an intermediate level, where you know the mechanics of the language, and you can generally converse with French speakers.
If you're looking to to beyond this and reach an advanced level of French (e.g., enjoying friendly banter with French speakers and understanding all their jokes, watching French TV and movies) you'll need greater exposure to "real world" French input than a grammar course alone can provide.
The best solution here is to move to a French-speaking location — but obviously not all of us can do that.
If you're hoping to reach this level through self-study at home, you will need to start exposing yourself to a wide variety of French resources as early as you can manage (without intimidating yourself). Be prepared to experience the intermediate plateau, which largely comes from needing a more varied diet of French input.
If you need French for work, you could supplement your general grammar course with a "business French" course or book that will give you more work-related phrases, business-culture insights and vocabulary.
If you're hoping to pass an exam or qualification, you should avoid the "contextual" grammar courses and choose a academic grammar course that clearly explains the grammar. If your grade includes a written or spoken assessment, you'll want to focus on building strong skills here — think about using a tutor to make sure you get it right.
For travel and conversational French, an understanding of the grammar is still important. You could use a contextual grammar course if an academic-style course is too dry for you — it may launch you into more conversational language a bit sooner too.
In everyday situations you'll probably encounter a lot of casual and spoken French — which can differ significantly from the "proper" French you'll learn in a French course. You can take additional "casual French" courses to prepare yourself if you want to hit the ground running.
The combination of your time frame + your goals will determine how hard and fast you'll need to study, and how you'll prioritise your learning material.
If you need to be up and functional in 6 months so that you can drop into a French-speaking location ... focus on working through your grammar course and getting the main grammar rules firmly lodged in your memory. You'll probably sound formal and textbooky, but people will be able to understand you. You can learn the rest on the ground.
If you have a longer time frame (or no fixed timeframe) then you can take things easy. Mix up your grammar study with additional resources that keep things fun. Broaden your vocabulary through extensive reading, and you may be able to avoid the intermediate plateau.
A reality check: You shouldn't expect to reach an advanced level of French within 6 months. You may be able to reach an intermediate level, if you're diligent with your study. To move on from intermediate level requires digesting a lot of real-world French input, and this takes time.
In the next few sections we'll look at the types of courses and tools you can use to learn French.
Keep your goals in the front of your mind as we go, so that you can filter out the suggestions that won't work for you, and zero in on the ones that will.