Natasha,
The best method is one invented by a kitchen installer and now used by Franke - the G-Clip.
You can discover how it works on both stainless steel and ceramic at the following link
http://www.franke.com/kitchensystems/uk/en/home/product_information/franke_gclip.htmlI'm uncertain as to whether you are able to purchase this as a seperate item but it certainly works well to ensure the sink will not drop.
If you are unabl;e to purchase the G-Clip seperately then a method I used in the days before such timesaving inventions became available was to create a support frame using battens fixed to allow the sink to sit level with the top of the cabinet. This again will ensure that the sink will not drop yet is a rather more time consuming method,
You must apply a neat bead of Silicone sealant betewwn sink and top after using any of the above methods.
Hope thios helps and good luck.