When looking for proper collectibles, your best bet is to check with an antique dealer. These folks have extensive knowledge on vintage items and will be able to find and appraise the pieces you need. Antiques are old collectible items that are often desired either for their rarity, condition, or beauty. The term isn't often applied to anything younger than 50 years old. This can be applied to general things like furniture, toys, jewelry, and books. Some folks look for specific items, like glass lamps, china dolls, or revolutionary war guns.
The definition of an antique can vary from year to year, though any piece over 100 years old is often considered one. This can include works of art, pieces of pottery or porcelain, and any other ornamental decoration that may be considered valuable.
Dealers work directly with auction houses, stores, or independently to find collectibles for sale. Often they have to meet with contacts to act on behalf of their clients. Some dealers specialize in one aspect of the trade, so when looking for a proper agent, be sure to ask. If you're looking for a particular roll top desk, a grandfather clock, or a table from the 18th century, seek out a specialist who deals mainly in furniture. He'll be able to appraise the pieces properly to get you the best price. If you own an antique shop, you may want to work with these folks to get you stocked up on the best furniture (i.e. tables, chairs, etc.), glass mirrors, and vintage clothing. They'll also be able to help you seek harder to find things like heirloom rings or vintage maps.