I was not very keen to go to Legoland but it turned out to be an amazing place. My tips for a good trip are:
* If you think you will go at least twice in one year then buy an annual pass
* Be there for when the gates open (around 10am)
* Jump on the Hill Train to the far end of the park and work your way back
* Take your own snacks with you. There are lots of benches and picnic areas
* Take waterproofs for the wet rides (there are quite a few)
* Although the rides are height restricted some of the rides for little ones can be a bit scary eg rollercoaster
* Queues build up from lunchtime no matter what the weather.
* Don't try to do everything
Have fun!

Definitely worth getting the annual pass to go more than twice a year. To do everything in a day would be knackering and mean a lot of queueing.

Good mixture of indoors and outdoors to cater for the English weather, but take wet-gear.

Extensive rides (check how exciting they are as only the child's height is taken into account. We had a couple of surprises with our son)
Expensive, but if you get an annual pass for your child (and yourself) it is worth it.
Some long queues when park is busy - aim for a dry day, as most of the activities are outdoors.