There is a lot to consider when buying a new pair of Hiking/outdoor boots.
I would always reccomend any body to take time out and get your feet measured and take on professional advise if you can.
Your feet will thank you......and you will suffer less.
If you have a certain brand of sock you always like to use....take a pair along with you at the fitting.
Lacing your boots too tight will restrict blood flow this is when your feet get sore and cold.
Ask about insoles...so many types out there.
Use foot powder....just a dusting.
If you are load carrying especially....you will need good ankle support and a nice cushioned sole to absorb shock.
A good grip...beware because some soles are lethal on slippery surfaces such as rock even though they have good grips.
Look or ask for the usual...hard wearing...waterproof....breathable......and maintain them well
When you have made your choice give it time to wear them in....going on a 10 mile hike in brand new boots is expecting too much to soon