Some general business thoughts, though grab a couple grains of salt as my business education/experience is primarily NOT in food service.
Translating over though, ask yourself some of the following questions. If you don't know the answers right now you probably ought to be thinking about them.
Can you describe your customers? Who will be seeking you out and giving you their hard earned money? Why will they drive past other restaurants to get to
you? Are they picking up for take-away or eating the food right there? Is all the proper ancillary stuff available for either, ways to carry condiments such as sauce if takeaway or places to sit & ways to eat and clean up if eating onsite? What will they tell their friends / family / co-workers? Why should they come see you today instead of tomorrow?
Describe your competition. What other vendors or restaurants serve the same customers? How will they react to your presence in the market? What advantages do they have over you today and what advantages can they easily acquire over you tomorrow if they choose to? What advantages do you have over them? How will you maintain those advantages?
Do a SWOT analysis (which the above covers part of) for your venture; Strengths, Weaknesses, Opportunities, Threats. Do a similar one for your perceived primary competitors. Always remember that prepackaged stuff from the grocery store is one of your competitors.
Do a cash flow analysis. What will you be spending money on and when? What will your fixed costs be that you'll have to pay whether you sell a single meal or not? What will your variable costs be that change based on your sales volume? What is your total cost for each menu item at two or three anticipated sales volumes? What do you anticipate your daily/weekly/monthly sales volume to be and why? Will it be seasonal / cyclical and what will drive that? How will you cover your fixed costs during the slower times?
There's also a bunch to consider in terms of labor that you'll want to be thinking about too. Will you need help? Who will be working for you, how much will they work, what will your total costs be including all the myriad taxes/fees/etc. you deal with when you have employees.
Hope the above helps.