Live within your means, DUmmy, it really is that simple.
I once was a student and lived on very restricted income, so I had very restricted out-goings.
Then I had some starting out crappy paid work, I still paid off the overdrafts which I'd built up as a student by having few outgoings.
Now I have a significantly better paid job, dont have any debts and have saved some cash.
About to take a career shift which will lead to me never earning much, so I'll change my spending patterns to match.