If they are the non-denominated US stamps, there is an identifier on the USPS web site. For collector values, check an online catalog, such as Mystic Stamps.
These were provisional issues. The post office did not know what price Congress was going to let them raise the price to, so they printed stamps without a value. You can find the face value on the USPS web site and in catalogs.
An easy way to find good value for your stamps is to buy a stamp magazine. Linn's is a good one.
There are a number of online stamp catalogs available, some do charge a fee. Others have a catalog with prices to purchase stamps from them, but it can give you and idea of value.
You would find them in older businesses, legal firms and factories that have hopefully not thrown them out.
Use a catalog to find values. There are several available online, such as Mystic Stamps. You can also find paper versions at most public libraries.
The could be of value. It would require proper identification to find whether the value is more than just a nominal one. Consult a catalog of postage stamps to identify and determine value.
There is no easy way. You will have to identify the stamps and their condition and then match them against the catalogs to find their retail value. For many collectors this is the fun of collecting, hoping to find that $100 stamp in a collection they paid $5 for.
If you are on a tight budget and are looking for affordable cheap stamps I would start by looking at Walmart, Super Value and carousel checks. Those all offer affordable cheap stamps.
Online sites that have stamp value guides include Stamp Collecting Resources, Stamps Site UK, Hobbizine, Find Your Stamps Value, Stamp Treasures and Mystic Stamp.
It may have value if you can find someone to buy it from you. A postage stamp has value, but not anything that you can demand. You can't hand one to a clerk in a store and they have to take it.
That will depend on the specific stamps. Condition, face value, mint or used, heavy cancellations will all play into the value. You will have to consult a postage stamp catalog to find out the specifics.
{| |- | The first step is to identify the stamps. Consult a stamp catalog such as Scott's, which include pictures and descriptions of all the stamps. They typically include a price for the set as well as the individual stamps. It also provides details on identification as well as a description on how stamps are rated and graded. |}