We have started on the path of visiting schools even though our children are still very young but that's life in Dubai. The fact is there are not enough places for the number of school age children.
We were advised to put our 2.5 yr old's name down on the waiting list for 2-3 schools. Having your child's name on the waiting list does not guarantee a place. Plus schools are introducing a foundation year which means 3 yr olds need to get in so they can progress to the main school.
If you live in Mirdif, there is the added advantage of using schools in Sharjah whose fees are cheaper.