I started weaning Alex at 4 months because he had a reflux problem (but was also showing all the signs of being ready for weaning).
We started him for the first week just giving him a small pot of food after his lunchtime bottle. It's best to give the food after the bottle because then you know that they're getting enough milk and then filling up on the food afterwards - otherwise they tend to fill up on food because it's more stodgy and not the get the nutrients they need from the milk.
My weaning schedule went like this:
Week One: 1 small pot of pureed carrots, sweet potato, parsnips at lunchtime
Week Two: 1 small pot of pureed apple, pear, banana at breakfast
1 small pot of pureed potato, brocolli, butternut squash at lunch
Week Three: As above but added in another meal at teatime - often more veg.
I didn't bother with baby rice as my hv said lots of babies don't like it and it's just as easy to start on the veg.
Just be careful, until they're 6 months old they shouldn't have anything with gluten in - lots of the baby food jars say they're suitable from 4 months but contain gluten. Also it's advisable to give your baby the same food for 3 days running to make sure that they're not allergic to it.
Hope this helps x
