There is quite a large number of yoga poses (yoga asanas) to practice and choose from. You can choose which ones to practice based on how you feel, on what part of the body you would like to target,...the choice is yours. They will each have a positive impact on your body and mind in their own way.
Always make sure to start a session slowly, with postures that will warm-up your body, as mentioned in the How to Start section.
Yoga poses can be chosen according to your mood or desires. Back bending postures, such as Sphinx Pose, Cobra or Upward Facing Dog, bring energy. They are a great pick if you feel tired and would like to feel more energized. They will open up your chest, your heart and lungs, allowing the breath to flow freely. They can be a great choice for a morning practice.
On the other hand, if you need a relaxing, calming practice, Forward Bends are one of your best choices. Folding the body forward helps to slow the breath down, to appease emotions and to release stress. A day is well ended with some calming forward bends.
You can also choose to orientate your practice toward strength. Quadriceps get a good workout with asanas like Warrior II, Right Side Angle and Lunge Poses. Lengthen your stance and sink the hips down to get more challenge. Your upper body will also get a nice work-out in these postures. Hold the pose for several breaths and feel.
Chaturanga, Plank and Side Plank are great examples of postures that will strengthen your arms.
Try building your yoga session with postures chosen from the different groups. And make a part of your session focus on a theme group if you wish.