Careful and accurate use of tenses is important for clear writing. Even the simplest narrative describes actions that take place at different times; when you use the appropriate tense for each action, readers can follow such time changes easily.

By the time he lent her the money, she had declared bankruptcy.

Use an infinitive (to plus a base form: to go) to indicate actions occurring at the same time as or later than the action of the predicate verb.

Each couple hopes to win the dance contest.

The hoping is in the present; the winning is in the future.

Use a present participle (base form plus -ing) to indicate actions occurring at the same time as that of the predicate verb.

Seeking to relieve unemployment, Roosevelt established several public works programs.

A past participle or a present-perfect participle (having plus a past participle) indicates actions occurring before that of the predicate verb.

The past participle flown shows that the flying occurred before the joining.

He launched the war after he crushed the opposition.

One common error is to use would in both clauses of a sentence with an if clause. Use would only in one clause.