What is the tone if the word has no accents?

If there is no accent on a syllable in a word, usually you do the opposite of what comes before it. This is why it is sometimes called the contrarian tone. If the one before is high you then go low. If the one before is low then you go high. It is also short and with a soft enunciation.

For example if the first syllable is 1st tone followed by no accent, you should go as low as the first tone is high. 
Graphically you would have:

If the first syllable is a 3rd tone followed by no accent, the first time is low, therefore you go high. 
Graphically you would have:

This is true of the 2nd tone, if you end high, you'll go lower. This too can be shown graphically:

The only exception to the rule is when you end a 4th tone. Just repeat the pitch at a low tone and pronounce quickly and lightly. 

Summary

Below is a summary of how to pronounce a word when there are no accents.

Alternatively

An alternative to remembering this rule is that when there is no accent go low, except when there is a 3rd tone.