Some people begin with a more flexible fate then others. Changing ones schedule around or going to bed an hour earlier are possible solutions. Beginners can try setting aside a consistent amount of time everyday at the same time of day and following through even if they don't feel like it. The commitment itself actually makes things easier. The best qi of the day for practice is early morning, between 3am and 8am, but other times are also okay.
Then there is the topic of where to practice. Some knowledge of fengshui is helpful here. The basic idea of fengshui is that the site itself is the most important consideration. Since you will be taking qi(inspiration) from the environment, the best location is a place you want to be, and that you can come to consistently. A place where you feel safe comfortable and can be alone. It should be a place where the air is fresh(free to circulate) yet still (absence of wind).
If your practice location is too cold your circulation may slow down, but it can also be drawn in to a deeper level. Cold places can be fine if they are not damp or wet and you are bundled up and out of the wind. Wind easily disrupts weiqi, the qi on the surface of our waking body. A healthy person will develop weiqi which complements the environment they practice in. The human body is adaptable; however, the effect a particular environment is having on ones practice is of vital importance and requires regular reassessment.
The classical ideal of the perfect place to practice is in a southward facing valley surrounded by gently slopping hills on three sides with the highest point to the north. A traditional Chinese walled garden attempts to replicate this environment in an urban area. The light well in the center of traditional Chinese architecture also tries to reproduce this qi experience.
Considering the totality of your experience over time, you may want to avoid the following:
Open corridors, or pathways where people or animals are likely to walk by.
Standing in direct sunlight in mid-day
Stagnant water, mosquitoes
Things that look like they could fall
Where people are sick.
Even expert knowledge of fengshui can not overcome a 'bad' site, the first consideration should be the quality of the site. People who find a great place to practice dramatically increase the likelihood of bringing their practice to fruition.