One way of evaluating ideas would be to use a simple scoring system using gut-feel with a limited number of criteria as shown below.

Before scoring individual ideas, run through the criteria and set what you feel should be minimum desirable scores for each. The resultant total could be used as your overall minimum threshold. If some ideas don't achieve satisfactory scores, drop them and look for better ones.

Once your short-list has been developed, you will need to start devoting substantial time to assessment, research, development and planning.
You could pursue the following tasks:

Discuss products/services with prospective customers
• Assess the market using desk & field research
• Analyse your competition
• Consider possible start-up strategies
• Set ball-park targets and prepare first-cut financial projections
• Prepare a simple action plan

more ....