What to Wear?
Remember to wear comfortable clothing that is non-restrictive. Jogging bottoms are fine although I may need to see what your legs are doing so shorts or leggings are better. If you are in a hot climate dress accordingly as we can get pretty sweaty. Try to keep jewellery to a minimum (non if possible) as adjustments are made during the class and they can get in the way.
Eating
Don't eat a large meal for over 3 hours before a class. Small meals can be eaten an hour before a class. Some of the postures can tone the inner organs too and this can be uncomfortable if you have eaten recently.
Equipment
Mats are supplied in some places I teach though not all. Sometimes you will need a block or a belt. Again, sometimes we have them depending on the shala. If you decide that yoga is for you, then it is a good idea to get your own equipment eventually. That way you can do more yoga at home. And the place you really develop your practice is on your own mat in your own time! Try the Yoga Shop a fantastic website to get all your equipment from. Links on the last page.