Not hard at all.
First, look at the 3rd person plural: читают, пишут, любят and so on. Remove the ending.
Done! Читай, пиши, люби. To make it plural or polite, just add -те: читайте.
This lesson deals with the И-pattern plus some irregular forms. However, the pattern described above works for the vast majority of the verbs. The irregular stems give you ешь, дай, беги.
Which aspect to use? Well, if you focus on the process ("Please, slice evenly") or encourage engaging in some activity, use imperfective. Otherwise, especially If you want to get a result or a single specific action, use perfective.
When forbidding something, use the imperfective.
You may notice that sometimes when Russians want a specific action (let's call that "simple request"), they still use imperfective. Why? Here is the prototypal meaning of such usage:
By the way, that "obvious" point is why imperfectives are not, as a rule, used for detailed "simple requests", especially with "please". It is OK for some typical guest-receiving situations ("please, come in", "please sit down"). But IMP. is out of question with clearly non-obvious detailed requests like "Take my cat from the sofa, please" — how can such thing be obvious, and if so, why would you ask in such detail? These two contradict each other: appealing to the listener's common sense ('You should obviously do that') while at the same time using 'please' and giving the details.