Really, the best things you can do are take care of your hair, eat healthy and be patient.
Use deep conditioning treatments once per week, penetrating oils, sulphate-free cleansers etc. Only comb/finger detangle when your hair is covered in conditioner or coconut oil.
Make sure you're getting enough vitamins and nutrients. Some people take vitamins, others drink protein powder. But really, a balanced diet does the same thing. Like your mother always said, 'eat your fruits and veggies!'
Don't keep staring at your hair waiting for it to grow.
Thing is - healthy hair grows long and unhealthy hair breaks off. So nurture your locks and enjoy the journey and your hair should start growing nicely
Yes, a healthy diet and moisturizing is important. Also, I like to use lavender oil in my hair. It works pretty well. So does massaging your scalp, which helps circulation. Keeping it clean is important, too.
If you want instant long hair you can use hair extensions. The best hair extensions are those which are most compatible with your own hair type, texture, color and current condition. I get mine from Glamorous Lengths.
I've been growing out my hair for about a year now (3B-3C mix, medium porosity). One thing that really helped me was massaging my scalp with coconut oil and sleeping with it (with a bonnet on so it) and then shower in the morning. This really served as a deep conditioner for my roots and I think that had the most impact in growing my hair from around bust length to elbow length (6 inches once dried)
One thing to consider though before putting in all of the work growing out your hair is how important volume is to you. I had very voluminous hair before and loved that it was so big and I definitely didn't expect the insane loss of volume (although it does make sense that it gets heavier the longer it gets). I have some layers (the shortest being around chin length when dry), but I have so much less volume than I did before at (hair around bust level) that I'm seriously considering chopping a good 6-8 inches in order to get my big curly hair back.
Does anyone have any tips on how to get volume in long hair? I try not to use hairspray or anything very "grippy" very often because it causes tangles.