I start with a few minutes and get to consistency with that. It takes practice, then I am able to do longer time periods, so I add 1-2 minutes at a time and build up. I also use guided meditations that focus on the topics I need help with or that seem relevant given how the day went, etc.
I'd like to be able to meditate for 15 minutes. Currently I manage about 2 to 5 minutes before I get severely distracted.
My length goal for meditating would be to practice everyday when I wake up. If I miss one time meditating in the morning, I may meditate in the evening. But I want to try to meditate at least once everyday for 10 minutes.