The problem I always experienced when coaching my daughter (and I did so MANY times) was that I was too focused on what she was or was not doing and not at all focused on what her opponent was or was not doing.
Between rounds I was always saying things like "Why aren't you doing..." or "Why the hell are you doing..." when I should have been like "That girl is doing... and you need to do... to compensate" etc.
I always told myself before every fight that I was going to focus more on the other girl but when the fighting started I always focused 100% only on my kid.
You were on the right track Mango. You are aware of your short coming and only need more time (experience) coaching to get better (develop). You should maybe have started with someone other than your daughter. Once you have developed better coaching skills you can then come back to coaching your daughter
Erik, the more you do anything the better you become. One thing you can do is to watch other good coaches. Sit next to them when they coach and see what they look for and what they do. I know at local tournaments you can sit behind or stand next to coaches at the ring (as long as you don't interfere) and pick up some great tips. It is also helpful to have a good coach let you coach and then after point out things that you may have over looked. Also watch coaches that are not so good also and try to give advice. Even when simply watching matches of others you can arm chair coach and bounce ideas off of others that are watching with you.
Nothing comes overnight. It takes time just like anything and the more you do it the better you will become. As Master Terry said, video tape the matches that you coached and watch them back. Look at where you maybe could have done something different. Never toss the videos away as you can come back to them months and years later and still find even more opportunities that you did not see each time as you experience gets better.
Coach all different skill levels as well. Better fighters may see and do things that you do not see and the lower skilled will give you the opportunities to hone your basics. I still watch all my sons and daughters older matches over and over as I always see something I missed before. I even watch their matches from when they were color belts. This gives me understanding of what those levels need to be working on and keeps me grounded at all the different levels. Sometimes coaches expect green belts to do and see what black belts see. They don't and you have to understand that.
One tip that I can give is to look for types, Aggressive vs. Defensive vs. Balanced. Then work on understanding what is needed for each type you coach against.
The easiest to coach against is the Defensive fighter. The next is the Aggressive, and the hardest is the Balanced fighter. Look at each type and learn to define the opponent right away. Then have game plans for each type.
Also you should be able to tell if the opponent is right or left dominant pretty quickly also. If you can pick up on these two things pretty quickly you should be able to give your fighter this info giving them some knowledge to help them. Your fighters should be looking for that same info right away also.
Coach before the fight as much as possible. This means that during your training with your fighters you should be teaching them to coach themselves. You should not need to talk that much during the fight and in between rounds you and your fighter should already be on the same page and be seeing the same things. You are there as an extra set of eyes to maybe see the one or two things that the fighter does not see. You are also there to help motivate.
My son gets to tense sometimes before a match and will try to hard. At the past J.O.'s I saw this and between matches I felt that cracking some jokes would loosen him up. It did, and every time he step to the center of the match to bow before the start of the match I would just yell out the punch line to our inside joke and he would smile. I knew he was relaxed then. I was not even his coach in the chair but that little bit of coaching I did from the side made the difference.
Just get as much experience as possible and you will be fine.