When To Use Before Triggers And When To Use After Triggers?

1. Before Triggers:

To perform the validations we should use before triggers.

If you are updating any field on the same object on which you are writing the trigger and no need to explicitly include the DML statemetns (already due to DML operation only trigger fire and it is still in progress at this point of time.)

2. After Triggers:

If you are dealing with relationship records and if you need record id in these situations we should use after trigger (in before insert record doesn't contain the record id).

3. For the same event if there are multiple triggers on the object, how to control the order of execution?

We cannot control the order of execution in this situation. It is recommended to have only one trigger per one object.

Note: We can keep the logic of the apex trigger in an apex class and can invoke from that class.

4. What are the recursive triggers and how to avoid?

If we perform update operation on the record in after update event logic recursive triggers will arise.

Using static boolean variable in an apex class (we should not keep static boolean variable inside of the trigger) we can avoid recursive triggers.