There are a number of activities to get ready to raid, and likely you will already have some of these done, you can consider this a checklist of things to accomplish, they are ordered in how long they take.
My first recommendation is that your first raid is as a DPS Specialization for your class, there are several reasons for this:
- In general DPS in Normal have the lowest personal responsibility for mechanics
- those that exist are often handled by the more experienced raiders.
- There are the most DPS slots
- DPS has the most resources and clear-cut ways to improve
- Everyone has a DPS spec so it makes it easier to write a guide or everyone
Also, any class can complete Normal, there is no reason for a group to bench you because of a specific class specialization.
Most of the advice will still work for healers the big change is around gearing/rotation, as a tank you need to understand all of the tank mechanics for all of the fights you are going to do and in general there is a higher level of choreography involved so I would recommend more time on researching the fights.