The best idea is the one that
A) you are passionate about
B) people want
C) is scalable

See below for further discussion:

"A" is useful because it helps ensure that you'll stick with your startup over time and through difficulties, and that you have an above average knowledge of the field to which the idea is being applied. This means that you will know how to best pivot the idea during development if necessary (always is), and it's less likely that someone else has already thought of your idea and is doing it better.

For "B", you'll need to quantify this in some way specific to your product. You can start with the idea that you think has the most market potential, but you'll need to quickly find out if _you_ yourself can make something that people want. That means making some sort of prototype which you can show people and gauge interest on (by collecting interested emails, by having them take the time to test the product and give feedback, etc.).

"C" is also important because coming up with a good idea that people like, and coming up with an idea that would be good for a startup are two different things. If you don't have a business background, always talk to one or two people that do, in order to hash out whether the idea is scalable.

There is a very simple way to think about this.

1. What are you good at? What skills do you have? What do you have work experience in?

2. Of the problems you have found which ones do you have subject matter experience with?

3. Then talk that about that specific idea with people around you. You will start with A by the time you talk to people you will be at Z

4. You need to make sure the problem is a large one and something people actually want. There is a difference between wants and needs.

If you say: Customer needs something
You have to educate them on why they need it which costs $$$$

If you say: Customer wants something
You can put a wall between them and they will go and buy it

Happy to chat further and dumb things down for you.

This is a broad question, which would really benefit from a much deeper understanding of where you are at and who you are as a professional, but here are a few tips:

#1
A good idea will solve a problem. You want to be building a pain killer, as opposed to a vitamin.

#2
Once you feel like you have a problem to solve, you should validate your idea. Here are some simple tips for validating your idea: http://www.startuprevival.com/7-ways-to-validate-your-idea/

I also recommend entrepreneurs to test the market by setting up a landing page and sending some traffic to it. Unbounce is a great tool for building landing pages.

With a modest budget (just a few hundred $) you can drive traffic to your landing page through Google Adwords. Try and get people to fill out a lead form or sign up for a trial of your product. If you get some leads, it will help you understand if there is demand for your idea. If you don't, it could mean there isn't a strong demand.

You could also buy some market research data using a tool like Survata.

#3
Once you have a validated idea that solves a problem, make sure it is something that you have 1. an interest in and are passionate about, 2. you could execute on with your skill set.

There are a lot of great ideas out there that solve problems. But it's important to make sure it's the right fit for you.

Best of luck!

You’ve got a great approach already, that is, finding problems and coming up with solutions. Now aside from any business advice I would give you, I would first of all echo Lee’s point about finding an idea that you are passionate about. Whatever you pick, you’re going to be working incredibly hard to get it off the ground and so it’s critical that you really care about what you’re doing. If you can find an area that really taps into your core values and interests, and even better where you already have both skills and experience, you’re going to be that much more likely to succeed.

I can’t help but pick up on your first sentence, that you’ve “been meaning to do a startup for over a year now”. What do you think has been stopping you? Is there something else going on, besides the difficulty of choosing a viable idea to focus on? Could there be some underlying fears or concerns about focusing full time on a startup that may likely fail? It’s worth addressing this mindset aspect in addition to doing the due diligence work from a business perspective.

In terms of validating your ideas, the only way you’re going to be able to do that is by going ahead and testing them. Call ten people in your client target group and ask if they would be interested in buying. Run some Facebook ads. Get a landing page up and see how many people opt in. You’re never going to be able to choose “the best” idea based purely on the theory and, in fact, there is no such thing, as it’s really all in the execution.

So ask yourself: what are you passionate about? where do your unique strengths lie? what experience can you leverage to give you a competitive edge? how will you be different to the competitors who are already out there? Based on your answers, go ahead and choose 2-3 of your ideas and test them.

Let me know if you’d like to jump on a call either to work through the business ideas themselves or, as I suggested, to look at other obstacles that may be getting in your way.

DO THEM ALL!!!
Maybe Starting businesses is really your business. Not running them.

Create a generic business name, corporation, and domain name, phone number, email, etc that can be used as a central location for every other business you may create. Call it ZAZA or whatever you want. Just make it non specific.

Start with your easiest idea. (One that you can do by yourself, requires the least capital, requires the least time, requires the least effort from you.) Remember "least" doesn't Mean "Little".

Bring it to a point of completion or to a point where you make a buck, It doesn't matter how much but making a dollars shows you have viable product people are willing to pay for.

Set your business in automatic mode by hiring partners, or outsourcing marketing ect so you can do this process all over again with your other business.

Maybe Starting businesses is really your business. Not running them. Your problem is very common among people who are multi talented.

The best companies arise organically - and aren't forced.

Startups are a deeply personal affair and are really tough. You should first be able to answer why you want to start a company. It can be materialistic reasons or for romantic purposes - but you should first know yourself (decently well) and why you're getting into this before you start anything.

Startups are incredibly high risk - and you've taken a leap of faith by quitting your job. Every first step requires a little leap of faith, so good on you for that. I took a similar leap in leaving school for a year to start my own company.

Like most things in life, there is no specific "get rich quick framework". There is, however, a logical approach that can be applied, which first starts by collecting your own data points through domain expertise.

I'd be happy to sit down, listen, talk these things out with you, and give my own personal examples. I started out with a logical approach, first collecting data of my own by working in various restaurants for many years before shaping the model/vision of our company.