i start my boy when he's 4+ months old. 1st food is apple puree (homecooked). think about 4-5 teaspoons. then he wants more. once a day for a few days. after that, i let him try spinach puree (also homecooked). also once a day for a few days to make sure he's ok w it.
you can go Popular bookshop to read the recipe book called First Foods. for some guide n reference. find it quite useful. 'cause it's based on local context.