Thanks Tanya-san for your answer, I was also unsure how to use ておく & てある.
@yurisaku
Funnily enough, today in school my Japanese teacher answered your question!
I took a photo of the whiteboard.
So basically with ~たら
-the action which you propose will take place, occurs AFTER the initial action.
So in the example うんてんしたら、じこをおこすでしょう. (If you drive, you may cause an accident)
The accident occurs after you start driving. Also たら suggests the action might happen, it's not certain that it will (unless you add an adverb such as ぜったい or きっと)
With ~なら
-the action occurs BEFORE the initial action.
So, うんてんするなら、れんしゅうがひつようです。(If you drive, practicing is a necessity)
In this case, you must practice before you start driving.
With ~ば,
I'm still a bit unsure, but I think this is always used in the present tense to indicate something that will happen in the future. eg from above: うんてんすれば、色々な所に行けます (If I/you drive, we can go to various places)
So that will occur in the future
With ~と
This is the same as たら but the proposed action WILL happen. So from above, うんてんすると、じこがおこります。(If you drive, you WILL cause an accident). It is almost always used in present tense, my teacher said it is not really used in past tense.
Hope that partly answers your question,
it was a quite hard one, I'm not too sure I understand it completely myself still.