tenses dilemmas

Teacher: Today we’re going to talk about tenses. Now, if I say I am beautiful, which tense is it?
Student: Obviously, the past tense.
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As tenses are a never-ending source of bafflement for students, here are some of the most problematic tense rules in a nutshell. However, before you turn your attention to them, remember that no rule is written in tablets of stone.

1. Present simple and present continuous

Present simple is used with verbs which perform the action they describe such as admit, apologise, guarantee etc. These verbs are sometimes referred to as performatives.

Present continuous is used with adverbs such as always/constantly/continually/forever to draw attention to something that is done so often that it is typical of a person, group, or thing:

You are constantly changing your mind.

If the verb consider means "think carefully about" it is used only with the present continuous:

He is considering taking early retirement.

2. Past simple and present perfect

If we have a sentence with the time clause since we use the past simple in the time clause and the present perfect in the main clause:

She hasn't been able to play tennis since she broke her arm.

If we have a time clause introduced by after/when/until/as soon as/once/by the time/the minute/second/moment, we use past simple if the time clause describes a past event and present perfect if it refers to the future:

After she left hospital, she had a long recovery.

I'll contact you the minute I've got the election results.

3. Present perfect continuous and present perfect

Present perfect continuous is preferred if we have a sentence were we draw a conclusion from what we can see, hear etc.

You've been eating my chocolate, haven't you? There's some on your shirt.

If, on the other hand, we refer to a result of an activity, the present perfect is used:

I've used three tins of paint on the kitchen walls.

4. Will and be going to

If we predict something based on our opinion or experience, will is used:

The children will enjoy seeing you again.

If the prediction is based on present evidence, be going to is used:

The sky has gone really dark. There's going to be a storm.