well you need to "come up" with the ideas yourself, otherwise an idea could be considered the intellectual property of someone and they won't give it up freely.
to come up with it on your own you need two things:
1. experience and familiarity with the field that you want to enter. this means hanging around, using different services,... to see how they work, to find where something is lacking and whether there is room for any improvements. of course there is also a big difference between wanting to make money from the idea or just wanting to innovate a useful tool.
2. having skills. after you found the opportunities and the lacking stuff, you have to look to yourself whether you have the skills to fill the gaps or if it is a business you want to run whether you have the skills to run a business.