TREE POSE (VRKSASANA) :

•Start in Mountain pose. Pick up your right foot with both hands and place it gently on the inner left thigh muscle.
•Turn the foot so the bottom of the foot is facing out (like standing half lotus pose).
•Hold the foot with your left hand from underneath and gently place your right hand on your right knee helping the knee go slightly out and down. 
•The hip opens like a hinge and the knee swings back like a gate on the hinge.  Don’t force the knee back; instead focus on releasing the hip.
•Your right knee should eventually line up with the standing knee from the side view.
•Tuck your buttocks under into a neutral position, stomach in, muscles taut, standing tall as if lifting your head and neck toward the ceiling. 
•If your foot is sliding, continue to hold it from underneath with your left hand for better leverage and bring your right hand to the heart chakra in prayer position (fingers together pointing to the ceiling, thumb touching the chest).
•If your foot can remain on your thigh, bring both hands to the heart in prayer position, Namaskar.
• Hold for twenty seconds.

JIMMY'S TIPS:

Many people in the Hot Yoga world refer to this posture as TADASANA, which literally means Mountain pose. Bikram and most likely Bishnu Ghosh, Bikram’s teacher, nicknamed this pose Mountain. But the actual word for tree in Sanskrit is Vrksha. Names of yoga postures are given for various reasons. Some asanas are named by positions: Dandayamana Janusirsasana, meaning “Standing head to knee pose”. Others are named after Deities: Ardha Matsyendrasana, “Half Lord of the Fishes Pose” (Spine Twist). Some asanas are named after animals: Camel, Rabbit, Cobra, Tiger, etc.
In Calcutta they speak Bengali, their interpretation and dialect is different from Hindi (the most commonly spoken language in India, except for English). For example, what we call The Wheel Pose, or Chakrasana in Sanskrit, other styles call the Upper Bow or Urdhva Dhanurasana; what we call The Frog Pose - Mandukasana, others call Full Tortoise - Poorna Kurmasana. There is no right or wrong, it’s all about interpretation of an ancient science so old it’s impossible to trace the origin. 
 
Beginners:
If you have any existing knee issues, be very careful and modify by bringing your foot only as high as your knee will allow. Go slow to avoid any discomfort or strain and hold onto the foot with the opposite hand for support. Another modification is to place the bottom of the foot on the inner thigh and turn your knee out to the side. You will still be able to open the hip and avoid any stress to the knee. Focus your eyes on one point (this is called Drishti in Sanskrit) on the floor about eight feet in front of you for better balance.

Intermediate:
Before you bring both hands to your chest in Namaskar, assuming your practicing the right side, hold your right foot with your left hand and raise your arm hand up toward the ceiling. This will help lengthen your upper torso, creating space between your ribcage and hips. Then place your right hand down to your chest in Namaskar. Don’t let your back arch, scoop your tailbone and buttocks cheek down to a neutral position.

Advanced:
Make sure your heel is directly below your navel. Many students with flexible hips bring their foot too high. Placing the heel underneath the navel allows you to square and open the hips. Visualize your hip as a hinge and your knee as a little gate that swings open according to the flexibility in the hips. Don’t force the knee, release the hip instead. This will take most of the pressure away from your knees. Assuming you’re practicing the right side: first extend your right knee toward the right wall, then work it back. This will raise the right hip thus squaring both hips. Proper alignment in this case is symmetric: your shoulders, hips, and knees are square to the front mirror.