It's a 'depends' answer, as with many things. 'Best way' is so subjective, that it really ought to be 'best way for Me'. I don't know anything about you, so here's a little overview of what I've learned in my time here.
Salaries are still reasonable these days on most places on the totem pole (not as good as before the TP-nerf), starting is around 3 - 5 mil monthly among the various factions that actively recruit constantly and need members. Salaries are a nice steady income stream, and often you can get a Sitting gig for in or around that same starting salary that'll let you do what you want as long as you just log in and sit in that faction.
Production is a risky business and has a lot of costs associated with it, but the profit can be very significant when you do it right. It's tempting to go for the Biggest ships possible, but they do take a long time to build and sometimes the price that you can sell it for when it's U/C or completed is not what you think it's worth now. Couple that with the startup costs for building SYs, etc. and you may want to consider alternative arrangements, including partnerships with others to use existing production resources.
Facility Income is a constant drip every month (when it works, that is) and is basically the only Income-generator for everyone. It provides the "new" credits into the system, which trickle down from the FI-owners (mostly Factions with FI-planets) to their members/employees. If you have cash sitting around doing nothing and you're not going to use it, consider investing in FI-facilities. Prices are grossly inflated for purchasing them outright, so if you can get away with it, build them yourself. Else, you'd have to rely on selling them later on for at least what you paid for them to get the slight gain.
Hunting/selling Trophies & drops:
- This ones favoured by a lot of people. You can actually make a couple mil very very easily just hunting creatures (which is NO risk if you do it right). And if you go after bandits and get lucky, some rare drops can net you a good 10-40 million profit from selling it to someone else.
- The best traders are hugely successful, but even they do the Production gig (or rather, pay others to do it) to maximize their profits. They do entirely rely on other people being willing to buy, though.