Why is this so hard if the pattern is simple?

Because most European languages use a single verb for both, faire, hacer, machen, fare, so there is nothing in the first language to split. Speakers of those languages are not choosing wrongly; they are choosing at all for the first time, on a distinction their grammar never asked about.

Which collocations should I memorise?

The ones that break the pattern. Make the bed, make friends, make money, make sure, make a fuss on one side; do business, do damage, do your best, do time, do someone good on the other. About twenty phrases cover nearly all the exceptions worth knowing.

Is “do good” different from “do well”?

Yes, and both are correct. Do well means to perform successfully. She did well in the exam. Do good means to have a positive effect on others, the charity does a lot of good. Swapping them changes the sentence entirely.

Which one to useA2

Do vs make

The short answer

Do covers tasks, jobs and unspecified activity: do the washing up, do your homework, do something. Make covers creating and producing something that did not exist before: make a cake, make a decision, make a noise. The pattern holds for most cases, and the rest are collocations.

At a glance

Do or Make?

Compare	DoTasks, jobs, unnamed activity.	MakeCreating or producing something new.
Core idea	Carrying out an action	Bringing something into existence
Typical objects	work, homework, the dishes, a favour, business	a cake, a decision, a mistake, a noise, plans
Vague words	do something, anything, nothing, well	Not used
Chores	do the laundry, do the shopping	make the bed: the exception
Speech and sound	Not used	make a comment, a call, a noise, a speech
Effort	do your best	make an effort

How to choose

Ask these, in order

1
Does something new exist afterwards?
Make. A cake, a plan, a decision, a mess, none of them existed before.
She made a suggestion that saved us a week.
The suggestion did not exist until she made it.
2
Is it a task, a job or a duty?
Do. The thing already exists; you are performing an action on it.
I’ll do the dishes if you cook.
The dishes are already there.
3
Is the object vague, something, anything, nothing, a lot?
Do, always.
We have to do something about the noise.
No specific object at all.
4
Is it a fixed phrase?
Learn it whole. Make the bed and do business both break the pattern and neither can be reasoned out.
make the bed, do business, make friends, do a favour
Four collocations to memorise rather than derive.

Side by side

Each one, in full

When to use do

Tasks, jobs, unnamed activity.

Do covers performing an action: work, chores, duties, and activities named only vaguely. Do the washing, do your homework, do the shopping, do some exercise, do a course.

It is also the verb for anything unspecified: do something, do nothing, do more, do well, do badly, and that use is completely regular, so it is worth anchoring on. If the object is a word like something or anything, the verb is do.

What do you do for a living?

Do twice: auxiliary, then main verb.

He’s doing a course in accounting.

Undertaking, not creating.

Could you do me a favour?

A fixed phrase, and a common one.

NBMake me a favour is a very recognisable error.

Make

When to use make

Creating or producing something new.

Make covers producing something: food and drink, objects, and abstract things that come into being when you say or decide them, a decision, a promise, a suggestion, a mistake, an appointment.

It also covers speech and sound: make a phone call, make a comment, make a noise, make a speech. And it appears in the causative: that made me laugh, it makes me tired, where nothing physical is produced but a state is.

We need to make a decision by Friday.

The decision comes into existence.

I made a mistake on the form.

Mistakes are made, never done.

That film made me cry.

Causative, make plus a bare infinitive.

Mistakes to avoid

What learners actually get wrong

I have to make my homework.
I have to do my homework.
Homework is a task you carry out, not something you create. This is the single most common do/make error, and it transfers directly from languages that use one verb for both, French faire, Spanish hacer, German machen.
He did a mistake in the calculation.
He made a mistake in the calculation.
A mistake comes into existence when you make it, so it takes make. The same applies to a decision, a promise, a suggestion and an excuse.
Can you do a photo of us?
Can you take a photo of us?
Neither verb, in fact. Photos are taken in English, which is worth flagging because the do/make question distracts from the fact that a third verb owns this collocation.
Did you do the bed?
Did you make the bed?
The one chore that takes make, because you are constructing something out of loose parts. It is a genuine exception to an otherwise reliable pattern, so it has to be memorised.

Questions

Asked and answered

Why is this so hard if the pattern is simple?: Because most European languages use a single verb for both, faire, hacer, machen, fare, so there is nothing in the first language to split. Speakers of those languages are not choosing wrongly; they are choosing at all for the first time, on a distinction their grammar never asked about.
Which collocations should I memorise?: The ones that break the pattern. Make the bed, make friends, make money, make sure, make a fuss on one side; do business, do damage, do your best, do time, do someone good on the other. About twenty phrases cover nearly all the exceptions worth knowing.
Is “do good” different from “do well”?: Yes, and both are correct. Do well means to perform successfully. She did well in the exam. Do good means to have a positive effect on others, the charity does a lot of good. Swapping them changes the sentence entirely.