First off learn how to mine, most if not all of the mining missions the materials are only available with laser mining.
Look at the mission boards, make a note of what types of commodities and roughly what quantities are asked for but do NOT accept any missions. Go do some mining for one of the materials that are being asked for, return to the station, check mission board and then accept and complete the mission with goods that you have already mined.
Keep a good eye on INARA - Commodities page, a number of carriers are buying at a lot better price than stations for the same commodities as being regularly asked for on the mission boards.
I am a carrier based miner mining out in the black, I mine for both high value commodities and mission board commodities, when I return I sell to mission boards, stations or other carriers, dependent on prices and weather I can be bothered to chase the highest prices or just grab a fair price and run
Feel free to check my carrier link is in my sig, cargo is visible.