Keep any contact brief.
For now.
Don't have long, drawn out conversations.
That means, no 30, 40 minute calls.
That means no text-ing beyond absolute essentials such as childcare arrangements.
That means no lingering and chatting by the office water cooler (if you work with your ex).
Why is it so important that you both have so little contact at this time? For one thing, you don't get the chance to let your desperation show.
This way, you are less likely to be in a situation in which you could find you start begging your ex to take you back.
You are not going to give yourself the opportunity to get so relaxed that, you know, next thing you are telling your ex in fine detail, how you spent last night rolled up in a ball on the bathroom floor, sobbing.
That is absolutely not the image you want to project at this time.
Another thing, this way, you don't have much opportunity to get into arguments.
Now is not the time to be arguing about who's right and who's wrong about things that happened in the past, or things that are happening now.
Also, when you don't have the "luxury" of rambling on for ages, you find that you start speaking in a way that is very crisp and clear.
You express yourself better, and you are forced to think carefully about what you actually want to say.
This reason, perhaps more than any other - and the others are very important - is all the reason you need to minimize contact while you're trying to repair your relationship.
Because at this time, you cannot afford for your ex to take the things you say, the wrong way.
Neither can you afford to say things you'll regret (which usually happens when you've been chatting for a while and have relaxed into the swing of the conversation).