At the idea stage the only investment you're likely to get is from your friends and family.
Typically - speaking from experience - You have to prove your business model, have many active (happy) users, prove the size of the market, demonstrate your uniqueness, profitability, scalability and above all else prove that you have the right team and people behind you to execute on everything you say you will.
Everyone has million Dollar ideas but your idea is worth nothing until you take action and get traction.
I would also add that when it does come time to seek investment you should do your due diligence and choose who you take money from wisely. Will that investor be able to open doors, do they have experience in your industry and be able to offer sound advice when needed? An investor should be treated like any partner you would want on your team.