When to use the future tense
I've been taught that using the future tense can kind of be an "old-fashion" way of speaking, or is more commonly used in the written language rather than the spoken.
I've been taught to use more of the ir+a form. I've noticed though that sometimes people will say something like "te aviso" o "hablamos pronto" when they are inferring to the future, but without using the future tense.
Can anyone explain that to me?
In English we often use the future to declare some that we are going to do in the future. (no uncertainty implied).
As you said Spanish tends to use the ir+a+verb infinitive periphrasis for that context.
Spanish uses the future mostly to imply probability (may or might happen).
Heidita just gave us some wonderful examples of using the future tense with if clauses in the link below:
If the verb in the if clause is in the present tense Spanish normally uses the future tense in the main clause. Here the concept of possibility/probability is expressed.
Spanish used the conditional in the main clause when the verb in the if clause is in the past.
: Si usted viene en una cita..
And, yes, you are also correct that Spanish routinely uses the present tense where we might use the future tense in English.