Hunting for stamps on eBay is relatively easy.  You just got to ask yourself what am I searching for.  Some people collect by topics like Flowers, Minerals, Ships, Paintings, Aircraft, Airmails, Military and the list goes on ad infinitem.

What you want to do is to navigate to the Stamp category from eBays home page there is a list at left, click on stamps.  In the search category box enter your topic.  For Example Flower, you will get a bunch of listing that have flower mentioned in them in the stamp category, probably too many.  You can refine and limit your search by searching only the description, uncheck the box at left that says to search title and description.  You can also add search criteria for example mnh flower, mh flower or used flower. 

If you are collecting by country eBay has provided pre selected categories for specific countries and area.  Under stamps you will find categores for USA Spain, Portugal, France, Italy and Area, Japan China etc.  You can browse using these pre defined categories. 

There are thousands of items in these categories and what you really need is a stamp catalog you can purchase these on eBay unders supplies and books category in the stamp sub category.  Scott is the largest stamp catalog system in the USA, you can find these catalogs at many libraries in the reference section.  When you know the catalog number of the stamp that you seek you can enter that into the search box and if the item is listed it will come back to your in the search result.

 The search or hunt is part of the fun of the hobby it can help you build a beauful and important collection.  Good Stamp Hunting 2U