Depending on the type shelf you are wanting to hang and the amount of weight it would be required to hold there could be several ways to secure the shelf. If the shelf was to support a lot of weight it would be necessary to locate the wall studs. For light loads a simple wall anchor would be adequate and a toggle bolt would allow a much stronger mount. Either of these methods would require the drilling of several holes in the tile. A masonry bit will drill the glass and tile bit will lessen the chance of a cracked tile from drilling. After the type shelf and supports are decided, then measurements would have to me made mark the placement of the shelf bracket. Make sure the shelf will be level. Mark the holes needed to install the brackets. Drill the holes necessary for your choice of anchors. Install the brackets and add your shelf.
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The shelf being glass will make no difference. They will still attach the same. There are some glass shelves that are made to attach with suction type attachments but I have never seen one that would stay attached or hold much weight. Below are links to several sites that carry glass shelving.