Is it correct to use a plural noun before "one of the" and in the following sentence should I use "are" or "would be"? if the sentence is incorrect please let me know the correct version.
Participating in extracurricular activities such as sport events and being a proactive student to promote my university in terms of attending conferences and meetings to talk about the features of my university are(or would be) one of my favorite activities.
No, you should not use plurals with "one of".
Instead you could say:
A and B are two of my favorite things.
A and B are some of my favorite things.
There can be exceptions to the above rule when two or more things are treated collectively as one group. For example:
Fish and chips is one of my favorite foods.
As for "are" vs "would be", that depends on your intended meaning. "Are" is the present tense, while "would be" is a conditional. If you do not need to indicate any uncertainty or hypothetical context, then simply use "are".
