Congrats! I have 3 children under age 5, so I know everything there is about raising children
But my points:
1- To echo Tonkaman, explain and reason with them. Instead of saying "Thats a No No! go to your room! (spank)" say "Hey girls, see those cool 'pictures' you just 'colored' on my car with a rock? Those are actually scratches, and they hurt the car. Lets go get the polish, and I will show you how to fix it now" -true story
2-As already said 100 times.. Spend time with kids. I work at home, and I am convinced I could easily double my income if I were at an office.. But I don't get to be Prince Eric at an office.. Nor could I dance with the Princess Celestia at an office.
The electrical switch story from UT410 is a great example of time well spent. It counts and matters to them. Include them in everything you can. (fixin stuff, mowing the lawn, checking the mail, etc.)
3- Some days you will just have to remind yourself that you once wanted this..:wtf:
Our personal parenting style includes very wide boundaries for the children, with strict guide lines and consequences. "yes, you can explore the entire mountain, but If whistle you need to come back"
Pay close attention to well behaved vs problem children.. You will quickly identify different parenting techniques, and what works better than others.
Good luck!