hi, about milestones there are no specific guidelines, but there are warning signs that parents should get concerned and which drs expect parents to talk about.
here are ones from 7-10 months ---
1.at 7 months, has poor head control when pulled to a sitting position
2.at 7 months, is unable to get objects into his mouth
3.at 7 months, is not reaching for objects, putting his arms forward or by leaning
4.by 7 months, doesn't bear some weight on his legs,,when hold upright supported by parents hands.
by 8 months, can't sit independently or even with support is not able to sit.
for crawling, its ok to wait until 12 monhts ! it all dpends on baby body structure and bones.
also, it has alot to do with bone density...talk to your dr, if it bothers you,,he might want to increase the calcium intake in your baby diet and if you are bf then he might prescribe you some calcium suppliments...
when it comes to babies, always trust your instincts..god has gifted mothers with a remarkable sight when it comes to babies..you know your child the best,,
sometimes,It may be nothing, but if your child does have a delay, you'll want to catch it early so you can get a diagnosis and begin treatment,,if at all it is required..
also to consider, some babies skip the stages,,there is nothing wrong in it. but often we want our babies to go in route where every baby passes..
so talk to your dr,,if he is ok with his growth, there is no point in getting worried.
Good Luck
Regards

Thanks a lot Mam for your prompt and detailed reply,What things make me worry are:-
Firstly my elder daughter was too quick in the sense, she managed to walk independenlty when she completed seven months and she could easily walk four floors (stairs) in mid eight month so this comparison just disturbs me.
Secondly the things you have listed here I feel my son is perfect in these respects, his birth weight was 3.800 kg,hieght 52cms and head circum 36 cms and presently his weight is 7.400 kg, He is quite fussy eater but i do manage by preparing something different every 3-4 days so that he's happy with the taste.... he managed to contol his head when he was 5 mnths old as he had an heavier head that's what i felt.....Presently he recognises when called by name, looks for when we speak in the other room on hearing us, gets very excited and communicates in his language to his sister, reaches to objects by turning around with tummy in one place, holds his head high when he is on his tummy,gets very excited when sees colourful objects and just pulls them to reach towards his mouth with both hands, understands when we are at the door and reacts to reach to that person, reacts to songs, ryhmes and sounds of the birds(love birds) at our place...but makes no attempt to sit, i.e when kept on the lap he places both his legs on the floor and stands erect (we hold him) and when excited in this position marches on the spot i.e lifts one leg and stands on the another quickly, very quickly and when forced to sit back he cries very loudly and wants to stand back again....Now Mam tell me..is it possible to stand without sitting down as i fear that his legs should not bow...and one more most important thing is, Do babies which achive their milestones late will be able perform later say in studies,games or any other activities in the same pace with their fellow children, why i ask this is cause his b'day is on 30.12.2005 so when gone for the academic admission he will fit in the year when 2005's born will be admitted and he'll be the youngest in the class.
I take your suggestion and will talk to my doctor also in detail during this visit, anyways he is on a calcium supplement (Calsuper) for the past one month.
Thanks a lot!
Regards.

Please dont worry.my son didnt not sit or crawl in his knees.he was pulling himself upto 10 months and straight away started walking with support.every child is different and develope in their own way.