But I understand that this practice is very new to lots of people, so I'll share how I do it, and maybe that'll give you some inspiration.
Traditionally, strictly speaking, you should rise at dawn, sit cross legged on a cushion, and greet the day facing east with your meditation. Light a candle, have tea next to you, feel the sun break over your face.
I think that sounds wonderful. I know my limitations, however, and I know I'm not going to do all that. My rituals have to be less structured so I have less steps to back out on, less reasons to do it "later." How exactly do I talk myself into this every day?
Sleep is very important to me! My first hurdle in meditating was to make it a regular practice, and adding any kind of longish routine to my morning was destined to fail. After trying various times of day and physical arrangements, I made a big decision:
I Can Handle 15 Extra Minutes in the Morning
I realized that 15 more minutes of sleep wasn't going to make my day any better, and that losing 15 minutes wouldn't make my day any worse. This is a core belief of mine. When my alarm goes off, that's the thought that enters my mind.
I find that beginning my day with meditation makes for a qualitatively better day. I don't necessarily 'return to the mantra' during my day, but the day is decidedly better for the meditating. I also find that when I try to meditate before bed, my relaxed mind then drifts haphazardly all over the place and I have a lot of trouble falling asleep. So I, personally, recommend meditating first thing in the morning.
Maybe you're the person who gets up at 5am to exercise no matter what, always. Maybe you get up at 5am even if you don't want to. Or maybe you stay up till 5am and are just grabbing a couple hours before your day starts. The point is, there's lots of sleep styles out there, and lots of waking styles. My 15 minute rule may not resonate with you, and you may have to find your own reasons. But do find your reasons, it's so worth it!