I did my hardwood flooring installation myself with the help of an experienced friend. I will share my experience with you:
1. Put extra screws in the subfloor where it creaks. Absolutely necessary. Cost of screws is really nothing compared to the whole project.
2. Removal of the old baseboard is recommended although some installers may say otherwise. Install new baseboard and quarter-round afterwards. Paint them first before installation. (I did not install quarter-round everywhere. Just lazy.

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3. The hardest part is installing the flooring in tight space such as closets, doorways and narrow hallways where many cuts/rips are needed. Take your time on it if you are DIY.
4. Nosing installation is not easy and it requires careful measuring and good workmanship. Professionals do a better job most of the time. (better than mine but then you have to look carefully before you can discover my amateurish mistakes.)
5. For doorways, you should always undercut the doorjambs to accommodate teh new hardwood floor. Make sure the installer do that instead of cutting the flooring around them.
6. Another area to watch for is the transition area, that is the area where the hardwood floor ends and your ceramic/laminate flooring starts. My amateurish way was just installing a transition molding over the area. A good installer should be able to do without transition molding and make a nice smooth transition, in most cases.
Hope this helps.