Grammatically, “also” can stay in different places in a sentence and be correct, but… the place of “also” is important regarding the meaning and the emphasis of the sentence.
The purpose of also is to join two ideas.
Let’s say the first idea is that “I think something”
and the second one is “what I think”:
Look at the different places of also and try to see the meaning;
Also, I think that my father should buy a new car.
I also think that my father should buy a new car.
I think that my father also should buy a new car.
I think that my father should also buy a new car.
I think my father should buy a new car also.
The position of “also” changes the emphasis and the meaning.
What is “also” actually?
“Also” is an adverb, that’s why its best position is near the verb, but if you want to focus on other part of the sentence, you can change the position.
“Also” highlights the word near it.
Well, this is about emphasis.
When it’s not about the focus:
“Also” comes in affirmative sentences to add another one like the first:
Mother loves Al Pacino’s films.
Dad also loves him. I love sport. I also love a good meal.
“1. Also” comes after “to be.”
I am also your friend.
2. but before all other verbs.
I also run in the morning.
“also” stays after have or be and before the participle or verb+ing.
I have also finished the project.
I am also working a lot.
I can also play football.
I should also go to the doctor.