first before u read this, know that I didn't graduate with first class but 2.1 with a CGPA of 4.44. so u could follow my steps and add a little spice to it to achieve a better goal, not just in school but in every aspect of life.

First class graduates are already gifted or has a background knowledge of the course better than u do, or probably did a predegree program so they know what to expect in school better than u who is just a rookie, so whatever u do in life to succeed, make sure u already have a good knowledge of it, if u want to trade forex and u have no idea, u could just loose ur money.
So before u pick that Jamb form, try to know a little about the course, not to jump into medicine cos a lot of people study medicine, u could be WAFFed before u even find ur stand.

u must have a little love for the course or any other thing. for instance, u don't like Biology and knows nothing about it but u are really good in Physics, but cos there is little job in physics and medical doctors are respected, u decide to jump into medicine, MBBS deh wait for u o.

Having all these in mind, the rest is simple.
First u should have a goal, a long term(LT) goal but divide it into short term(ST) goals. let's say ur LT goal is 4.7 at the end of ur schooling and ur ST goal is 4.48 at the end of a semester and another 4.52 at the end of the next semester
secondly u should get to work: Having a goal is good but going to work is another thing, if u don't read, u can't get a CGPA of 2.5 believe me
thirdly Stick to it: This is the most difficult part, this is where the word consistency and perseverance comes to play, a time will come when u will be tired in life, cos there will be some failures here and there, yes I have failed a course before but that doesn't stop me from reading, also in my final year, I made the biggest mistake, I got tired of school and declined in my reading habit, that mistake made me miss first class by an inch
fourthly achieve ur goals.

in summary.
Just set a goal
Get to work
Stick to it
Achieve ur goals

Note, there is no particular formulae that works for everyone, and this may not work for u, u can just design ur own life algorithm.

1.Set a goal
2.Get to work

3.Stick to it
4.Achieve ur goals

You still talking to yourself

just my own thought

A first class student in Nigeria is a book student never forget that. The only first class students I will applaud are those who engage in extra curricular activities because it's not easy to combine both.
Most first class students I have worked with or talked with are one sided I swear. They only know their field and nothing more. I have met briilant ones who are up to date in poltics/current affairs, entertainment and business including sports.
Those who make second class upper most times have a better view things than First Class but earned that particular G.P because they never poured everything to their lecturers