Firstly, I think your first mistake was doing an (I assume) online logo design course. I know that I may have said this a few times in the past, but logo design in isolation is fairly meaningless. To produce a good logo, you need to understand branding. To understand branding, you need to understand design as a whole.
This is why a number of us ‘seasoned’ pros keep banging on about getting a good degree education then doing five years’ work experience in a studio environment.
You learn about how to generate ideas, lateral thinking, critical thinking, typography and how to make type say what you want it to say – well at least, the basics. Another twenty years and you may just begin to understand type. This is the start, there are so many other things you need to learn
Sorry if this is sounding negative, but unfortunately you are one of thousands, who are promised ‘take this course and be a pro designer in just 10 weeks’. It’s not so easy, I’m afraid.
Coming up with ideas is something all of us struggled with. Your brain is hard-wired to follow linear routes, to find patterns. It’s a basic survival instinct response. You need to learn and exercise the higher parts of the brain. Eventually we find our own techniques on how to make our own brains do this.
I am afraid your question simply exposes the gaps in online courses. On the upside, at least you understand that you are supposed to be able to communicate a ‘tone of voice’ as well as practical information. A lot more that many hopefuls out there have.
The other thing about going through a traditional degree education is, it will put you through some sort of vetting process. I don’t mean this horribly, but how do you know you have a natural ability? Paying your money and taking a course does differentiate between good and bad, talented and mediocre. The university entrance process does this. If your are not talented, you won’t get a place. This is not elitist, it is a tough but necessary part of design. There’s no point spending loads of money and a few years of your life on something you may not be good at.
Even if you are, you need to be guided through how to think. You don’t come to the other end a pro designer, but you will be equipped to think in the right direction. The next few years experience, will then put that into context. After that, you should then be in a position to do what you are trying to do now and create logos (as part of a brand identity).
A single course in logo design is just a start (in the wrong direction, in my opinion). You need to learn so much more before you should be out there selling your services.
Part of the thing you have missed out on will be the critique process, so one thing you can do is post work here and ask for specific help.
Asking open-ended questions like ‘How do I come up with ideas?’ is like saying, ‘How do I become a cardio surgeon?’ They are both impossible to answer in a forum post. For the second one, there is only one answer, ‘Get yourself educated’. You’d have to, legally. There are no online courses in bypass surgery that allow you to practice as a doctor. You need to learn everything first, get experience, then specialise in cardio-vascular surgery and learn some more. Same. There are no legal requirements to do so, but the same response applies, ‘Get yourself educated’. Then get experience, then specialise.
Not what you want to hear, I’m sure, but I hope it help clarify your thoughts.