I suggest that before you even begin talking with investors you have a defensible valuation. Something that both you and the investor can agree upon regardless of which valuation method you choose.
Two important things to keep in mind are pre and post money valuations. If your business is worth $500,000 and you need $250,000 do investors get 50% (pre) or 33%(post). Once you have the percentages worked out you can start working on returns. How will your investors be paid? What's your exit? How long?
Assuming your offering equity over debt, (personally I prefer convertible note in the seed stage) is everyone signing a proxy or will they have voting rights? Do you have one series of stock or are the investors demanding series A preferred?
Your goal is to give as little as possible while the investors goal is to get as much as possible both in equity as a percentage of ownership and return.
The more sophisticated the investor the more complicated matters become. For small investments under $1,000,000 I'd do convertible notes in the 15% range on a three year term assuming you can handle the debt service.
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A thinker sees his own actions as experiments and questions--as attempts to find out something. Success and failure are for him answers above all.
Friedrich Nietzsche