I do have some pointers.
Yoga is not about performance...throw away any anxiety you have about "being able to do the moves". The postures are about function not form, and they can all be modified to approximate the function. For example, knees can be bent, chairs can be used, and blocks and bolsters. In my current yoga class ages range from mid 20's to mid 60's. Your instructor should be able to modify anything you need.
You should never ever hurt yourself doing yoga. Listen to your body and only go as far as you are comfortable (e.g., in a twist). Injuries happen in yoga when people feel competitive.
Of the dozens of health benefits of yoga most on them are more about the breathing than the postures.
Find styles of yoga that suit you (your body, your energy, your spirit). There are many kinds ranging from hot yoga to yin. We have a "yoga day" once a year when all the local studios open up classes by donations...there are around 50 classes all told. I usually attend 5-6 that day. It's a great chance to try out many styles.
Don't expect to burn lots of cals in yoga, that's why I do other stuff. But the increased body awareness and relaxation help a lot with emotional eating.
And, yes, use your own mat. I have attended so many classes where I have seen people not clean the studio mats just them away dirty (even hot yoga), yuck.
Fitday start date 12/9/12
Fitday start weight 190
Highest weight Jan 2009 218
Lowest weight Aug 2009 175
Goal 160: ACHIEVED Aug 25/13 (now to figure out how to stay here)
If you do what you’ve always done, you’ll get what you’ve always gotten. –Tony Robbins