Use the Simple Present to express the idea that an action is repeated or usual. The action can be a habit, a hobby, a daily event, a scheduled event or something that often happens. It can also be something a person often forgets or usually does not do.
Use the Simple Past to express the idea that an action started and finished at a specific time in the past. Sometimes, the speaker may not actually mention the specific time, but they do have one specific time in mind.
Simple Future has two different forms in English: "will" and "be going to." Although the two forms can sometimes be used interchangeably, they often express two very different meanings. These different meanings might seem too abstract at first, but with time and practice, the differences will become clear. Both "will" and "be going to" refer to a specific time in the future.
http://www.englishpage.com/irregularverbs/irregularverbs.html
http://www.saberingles.com.ar/exercises/201.html
http://www.nonstopenglish.com/exercise.asp?exid=870
http://www.nonstopenglish.com/exercise.asp?exid=881
http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-4253.php
