I just feed at breakfast time. To be honest I used to use Ready Brek from 6 months, occasionally having weetabix. I did try some Bircher Muesli the other day but you would need to miss out (or whizz up) the fruit until they could cope with soft lumps and in the UK they don't recommend oats till after 6 months and tell you to use formula or breastmilk in cereal if you do give it before 6 month (but I know this varies from country to country!)
http://mamacook.blogspot.com/2011/09/bircher-muesli-for-babies.html What's your motivation for making your own? I think before 6 months I would use the stuff specifically for babies but after 6 months I'd make sure I was choosing something without sugar or salt and mushy enough but apart from that, I'd just give 'normal' cereal with full fat milk. I'm not sure there's any real benefit in grinding your own and I think oats are treated with steam to make them more digestible and cut cooking times when they're rolled?
That all said, I am very much a fan of making other foods myself. If you're going down the puree route, I definitely recommend giving veg and fruit purees a go.
As for the mealtimes, I tended to give cereal at breakfast and sometimes bread at lunchtime when he was on finger foods or pasta at one meal but it was more giving 'a carbohydrate' rather than deliberately choosing cereals. Potatoes and rice are fine too.