Blogging questions

I am pretty new to blogging and I have a couple of questions that I was hoping someone could take the time to answer for me.

I notice there are a lot of PR/Giveaway opportunities and I think I would like to try this out for 'birthday season' at my house, which is when 4 out of the 5 members of my family have birthdays just over a week apart. I think it would be fun to host a little blogging birthday party with some fun giveaways.

How do you ladies go about it? should I take the initiative and contact the companies that fit well with my blog and just ask them???

Part 2

This brings me to the second part of my question, when mommy bloggers host giveaways who actually foots the bill to send the 'prize' to the winner??? I've seen some pretty, heavy and big prizes that would cost a fortune to send, but also it's not cheap to just send a parcel across the country so are moms willing to spend the money on mailing in return for the opportunity to try a product?

Part3

to roll along there with number 2 (sorry for so many questions) I've noticed some blogs state you need to live in the USA to enter their contests, is this due to shipping costs that they are incurring or for some other reason. I live in Canada and often can't enter giveaways, but would like to host some.

I know that was a lot, so I appreciate any help a kind member has time to give me!