STEP 1: DEFINITION

English has three time frames: past, present, and future. Each of these is divided into simple, progressive, perfect, and perfect progressive. The regular verb TO MAKE is shown below:

PAST PRESENT FUTURE
Simple = made Simple = make/makes Simple = will make
Progressive = was/were making Progressive = am/is/are making Progressive = will be making
Perfect = had made Perfect = has/have made Perfect = will have made
Perfect Progressive = had been making Perfect Progressive = has/have been making Perfect Progressive = will have been making

Each of these aspects is controlled, or affected, by time markers (also called time expressions or signal words). These are some examples of time markers which are commonly used:

PAST PRESENT FUTURE
Simple = yesterday, the day before yesterday, last week/month/year, a few minutes/two hours/five years ago Simple = rarely, sometimes, regularly, always, every week/day/time/year, usually Simple = tonight, tomorrow, the day after tomorrow, later, next week/month/year, in 2005, for the next 2 years/days/months
Progressive = while, when, as, at that time/moment Progressive = now, right now, at present, today, these days, nowadays, currently, presently Progressive = in 2005, for the next 2 years/days/months
Perfect / Perfect Progressive = before, after, by the time, already Perfect / Perfect Progressive =since, for, already, yet, just, so far, until now, several/four/many times Perfect / Perfect Progressive = by (a future point in time), by this time next year

Verb tense errors occur when students do not correctly match tense with time expressions and when they cause inappropriate verb tense shifts.

Incorrect: We are living there last year.

Correct: We were living there last year.

Incorrect: She raised her hand and gives the wrong answer.

Correct: She raised her hand and gave the wrong answer.

STEP 2: PRACTICE EXERCISES

Practice 1 - Recognizing verb tense errors in sentences
Practice 2 - Recognizing verb tense errors in paragraphs

STEP 3: LEARNING MORE

For more information on verb tense, follow these links:
http://esl.about.com/library/weekly/aa122197.htm
http://www.chompchomp.com/terms/linkingverb.htm
http://webster.commnet.edu/grammar/sequence.htm
http://www.lingolex.com/simplepast/allverbs.htm
http://www.englishpage.com/verbpage/verbs1.htm