Like someone mentioned earlier opening business is extremely tough!
The first thing is find something that you genuinely like to do, work
in that field until you absolutely master it.
Then you need capitals, if someone gives you/loans you money you will
be very likely to fail. Anyway good luck getting a loan from a bank
If you save that money on your own you will be more careful with your funds therefore better chance of success.
It takes up to five years to establish a business, if you survive the first year
(80% failure depending the field) it will probably be very difficult to make ends meet so be prepared for some difficult time.
In most business there is no such thing as 8 hours/day it is more like 12 to 16 hours/day 6 days/week sometime seven with no prospect of vacation for a couple year.
Also be ready for your wife/girlfriend leaving you because have no time or energy left for her needs.
This is just a few thing on top of my head, don't forget making a good product/service is one thing running the business aspect is a whole different ball game.
This is just a few pointers there are tons of variables and even if you do everything right there is still no guarantee of success.
Ok it is memorial day and I need to get back to work