Simple
YOGA
Life
No gaps in the practice :)
Ideally, yoga asana is done with no gaps in the practice! What this means is that yoga is practiced everyday, and best if it is done at the same time everyday! Even a 10 minute routine that includes all the main parts (see below) is minimally enough. Anyone can find 10 minutes. If you can't, you might want to reconsider your lifestyle and priorities. Of course, longer is preferable as possible. A regular 30 minute practice brings amazing benefits and feelings of well being. Practicing asanas becomes as regular a part of the day as sleeping, working, and eating. Once you become accustomed to the routine, a missed day will be very much noticed.
This said, it should also be noted that two or three times regularly a week can suffice. And it has to be admitted that even those who only practice irregularly and occasionally still show greater flexibility than their counterparts who have never done yoga before, and this is regardless of age.
Classical hatha yoga asanas
Physical yoga asanas are best done on an empty stomach. Any time of the day is fine for practings asanas, although many prefer either early morning or evening just before bed. If practicing in evening, it is a good idea to focus on poses that are calming and relaxing rather than those that invigorate. A complete routine will include balancing, inversions, forward bends, backward bends, inversions, twists, and relaxation. Sequencing is also important. Some ideas for sequences are given at the end of this section. Ideas for short sequences (10 minutes) are also give in the Lifestyle section.
To get benefit from the poses, it is good to hold for 20-30 seconds, or longer if possible. To stay honest about time, an easy way is to use a clock with a second hand. You can also count breaths. The breaths should be slow and steady. Try to hold poses for at least 5 breaths.
Never force anything. Yoga is gentle, and if something doesn't feel good it probably isn't. Release the pose and note the sensation.