There are loads of other threads under this section, discussing the current advice on when to start weaning - current DoH guidelines are 6 months. If you wait that long, you probably can get away with a shorter period of pureeing everything you give your DS. However, a lot of HVs advise weaning earlier and it is a matter of hot debate on MN whether they are correct to do so.
FWIW, in the end we weaned DS at 20 wks - started on the first day with carrot puree, then the next day he had the same and a bit of pear in the afternoon. For the next 3 weeks he had 2 'meals' a day, and then moved onto 3. It seemed to take him about 10 days to get the gist of swallowing and taking things from a spoon, but then he suddenly seemed to 'switch on' to food and really enjoys it.
Portion wise, we are led by his cues - they basically won't open their mouths if they don't want to eat! At 6 months, a meal usually consists of between 3-6 ice-cube portions of veg, and a pear / half of a banana / a pot of Organix fruit puree. Now he can take bananas and very ripe pears mashed with a fork. If the pear is VERY ripe indeed, he'll eat it solid, with supervision!
We kept him on just fruit and veg until 6 months, when we introduced some lentils and chicken stock for protein. Most veg are fine, but avoid peppers, tomatoes, potatoes, and aubergine till 9 months, as apparently these are related to 'deadly nightshade' and contain a few toxins (according to nutritionist Lucy Burney).
We have decided to keep him off dairy and gluten for a year as there is a history of asthma on one side of the family. Gluten free alternatives like millet and rice pasta are good to make his diet more varied.
HTH. Good luck.