Side Crow (a moment with straight arms) into Dwi Pada Koundinyasana (two foot) into Eka Pada Koundinyasana I (one foot) into Eka Pada II.

This is a great sequence! Side crow needs to be a fairly comfortable pose to begin with. Make sure to keep the knees and ankles stacked. When lifting the feet away from the ground get them IN LINE with your knees. in other words, don't let them hang, swing your feet UP. this will engage your core, keep you compact, and allow for the straight arm variation (push the ground away with the heels of your hands and do a huge round (cat's breath) in the upper back).
Continue to engage the inner thighs as you extend the legs out into Dwi Pada. Keep the arms in full Chaturanga, chest extends, elbows in, gaze forward. Take the top leg back to enter Eka Pada. Keep extending the chest, spread the toes and expand through the back of the knee caps.
Okay, so this is where it get's (really) tricky . . .as if it hasn't been yet. . .
to switch your eka padas, think like 'lady like' crossing of the legs. you'll come back to Dwi Pada, but do the 'lady like' cross of the top leg over the bottom, nice and tight. this will allow the bottom leg to escape and extend back. odds are it may feel like a ton of bricks. TOTALLY NORMAL. keep practicing until the load lightens up!