I don't know where you're getting your advice.
Milestones largely happen when corresponding brain areas mylanize (sp?) and sort of spring online. It's the best system you can fit through a small pelvis, and there's not a lot you can do about it other then offer them stimulation.
Every kid is different. You should only worry if your doctor tells you to. More than likely your child will lag behind some things and excel at others, and almost all of that evens out in the end.
The thing about your first kid is this-- just about the time you get in the rhythm of what's going on-- they change it up.
The second kid is easier.