Now, patience. Leave the glass and pit under indirect light, near a window or under a grow light. Maintain the water level as it evaporates, and occasionally (every week or so) replace the water with fresh water. In about 2-3 weeks the pit will crack. In the next few weeks a stem will start growing and roots will shoot out into the water. Not all avocado pits will germinate, so it's recommended that you start more than one at the same time. If the pit does not germinate after 2 months, chances are it's a dud.
Leave the seedling in the glass container until the root reaches the bottom. At this time you can plant the seedling, but I prefer to upgrade it to a larger vase and let the roots grow out some more. To do this, snip off the top of the plant when it's about 6" tall. You will notice the root structure to expand rapidly in the last week or so. After the plant roots fill out again, it's time to plant.
Use a potting soil with good drainage to prevent root rot. With typical garden soil (Miracle Grow, etc) you won't have to fertilize until months 6+. Afterwards, you can either use a water soluable fertilizer every 2 weeks, or oscomote tablets every few months. Be sure to get the planter-type fertilizer, the garden variety may burn the plant. At this point you can keep the avocado as an indoor plant, or as an outdoor tree.
To keep it as an indoor plant, keep it inside, and trim the top as it gets too tall or bushy. To plant it as a tree, wait until the plant is at least 3 feet tall and has a thicker trunk. To increase the sturdiness of your plant, shake the main trunk vigorously every once in a while, i.e. when you water. The little tree will not compete well with grass and surrounding foliage plants. As an outdoor tree it will require massive amounts of nitrates and warm humid temperatures. If your winters are below 45F, it will not survive until spring. An avocado tree is a large (20-40') tree, requiring regular pruning.