Esperando Que vs. A Que

Esperando Que vs. A Que
 

I can't find a rule and I’m unsure if I'm hearing "que" or "a que" in sentences like:

I'm waiting for the bus to come
Estoy esperando que/a que venga el camión/autobús

I'm waiting for my friend to come
Estoy esperando que/a que venga mi amigo

I have been waiting for you to bring me a coat
He estado esperando que/a que me traigas un abrigo

I would appreciate it if someone would give me a rule and/or clear up what I’m hearing or not hearing correctly.

Quick and easy rule:
If you hope that something happens, use esperar que.
If you're waiting for something to happen before performing some action, use esperar a que.

In each sentence you wrote, more information is needed if you choose 'a que', declaring what action you'll take when the thing you're waiting on occurs).

I really like the distinction that Rusty pointed out.

Estoy esperando que venga mi amigo. = I'm waiting for my friend to come.

Estoy esperando a que venga mi amigo. = I'm waiting for my friend to come first. (in order to do something, before doing something)

Thank you, Rusty and Tomisimo, for the concise rule. That’s great to have.

Rusty wrote:
In each sentence you wrote, more information is needed if you choose 'a que', declaring what action you'll take when the thing you're waiting on occurs.

I’m a little unclear on this. In using “a que,” are you saying the further action MUST be spelled out or can it also just be understood that further action will be taken, but I’m just not spelling out what that action will be? The example you both addressed focused on waiting for a person. If I don’t intend to tell you what we’ll do after he/she arrives, should I use “que” and not use “a que”?

Also, if I use “a que” when referring to waiting on a bus, do I still need to declare what action I’ll take when the bus comes? Can it just be inferred that when the bus comes, I plan on taking the normal action of getting aboard and riding the bus and/or opting not to give any more information about what I’ll do when the bus comes?

I have had this "esperar que" and "esperar a que" question in mind for a while, so any further clarification is appreciated.

All I was saying was that 'a que' indicates you'll do something when something else occurs. If it's understood what you'll do, there's no need to supply that information.

I always seem to remember examples better than rules, so it might be helpful to think: "esperar a que [subjunctive]" = "to wait until."

Voy a esperar a que venga (antes de hacer algo). = I'm going to wait until she comes (to do something).

Thank you, Rusty. Thank you, Tomisimo.