first, be aware that many parents base their own prejudices on what a school was like in the area when they were at school.
Schools can change massively in 10 years, so if you do gather opinions of others, it is worth asking what they base it on.
Secondly, every child is different and what they need at school is different. My ds is very peer led and it was very clear he needed to be in a school where it was cool to be clever. He is now at a superselective, competitive boys grammar school, and is thriving.
dd1 on the other hand is very self sufficient and couldn't give a toss about what others think, but she is very quiet in class and tends to get overlooked, even though she is clever. We chose a school for her which was academic, but very strong on pastoral care and a calm working environment. It also happens to be a grammar school, but our second choice was a good comp, where we felt she would do well.
Although your dd needs to be involved with the choice, it is a mistake I think to let the child decide. ds for example would never have chosen his school as it meant taking the 11+. he loves his school now and is really happy there. At 10 years old he simply did not have enough experience and understanding of education to understand the difference between schools.
Visiting schools is a good place to start, but beware. One really cool science lab where they set fire to your hands, or a D&T lab giving out free kitkat and your kid may be saying I love this school!
I found that I was swayed by the attitude of the school on open evening, did they want my dc?
I also looked at results, but carefully. By switching between raw results and English Bacc results you can make the top school in our area sink to bottom. Don't forget, that you cannot compare Grammar and non grammar directly either.
facilities, after school clubs, pastoral care, teams for sport, music lessons, etc are all things to look for.
If you do go down the grammar route, you will need to do some preparation in year 5. depending on your area, you may need to do a lot of prep.