I try not to cage my meditation with a kind/style or even duration.  In the beginning years I did practice Kriya yoga.  It is very specific with exercises, breathing techniques and duration.  I used to do mantras consistently. I found all of this very helpful in my beginning years. It kept me on track and developed my discipline.  But after so many years – my meditation has now just poured into my everyday existence. I connect rather quickly to my inner Ancient Mother space.  I can close my eyes and fall within this space a hundred times a day.  My meditation sits in the front of mind and is now my first ultimate truth – while everything else sits behind that.  If I find I forget – I read, I sit, I breathe, I do my asanas, I call out to my Guru.  I use all my formulas – until the truth reappears.  And usually this happens rather quickly.  With large moments of suffering it may take a day or two.  But I find now I can return home to my God space faster than before.  I think because I did plant the seeds so deeply before.   Sooooo, I would say start with 10-20 minutes a day.  Chose one mantra. Chose one breathing technique. Stay with this for some time. Months – years.  And when you outgrow it – you will know! You will know when its time to shift. Then one day – it will just become you.