What are the criteria for selling tokens?
The first thing to note is that test tokens (created on the Rinkeby network) cannot be sold. You can only sell live tokens created on MainNet.
Another important caveat is that test tokens cannot be moved to the live network. If you want to sell tokens, you need to first mint them on the live network.
Once you've done so, you can take ownership of your tokens by transferring them to a personal address that you control (for example, your MetaMask wallet). With the tokens in your wallet, you can offer them for sale.
Where can I sell tokens?
The most common place to sell tokens is on an exchange. Exchanges are decentralised (collectively referred to as DEX), or centralised. Getting your token listed on a centralised exchange is a difficult and expensive process. Most centralised exchanges will not list a new token unless it has high liquidity (lots of people already hold and/or use it), is well-known or otherwise has a high profile, and may require a substantial fee for listing the token.
On the other hand, access to decentralised exchanges is quite easy. Because they are decentralised, anyone can list a token. The methods for each exchange differ for each case, so it's worth investigating more than one DEX before choosing how and where to list your tokens. You ordinarily place a sell order on the exchange for some of your tokens, and if there is sufficient demand, buyers can choose to place a buy order (usually paying in ETH).
The price you set for your token is up to you - in the case of a token that you have created, you can choose the price that you want to sell for. Potential buyers can then decide if they feel the price is a fair one.
