If a customer gives details about what they're looking for, use that to your advantage: if you're uniquely suited to give them what they want based on those details, highlight that in your response. Recently I happened upon a request for wedding photography, which I normally don't respond to, but the customer detailed that they're getting married in the same exact (slightly unusual) place I got married, and we connected on that, especially because I understood the challenges of shooting there — and I got the gig.
If you're not uniquely suited based on those details, don't waste your time or potentially your money — because someone else probably is just right for the gig, and they'll probably get it.
If the customer doesn't offer details but you think it might be right for you, ask questions that can open the door to show them you're a good fit — the customer will probably appreciate your attempt to connect with them on a meaningful level. If they like you and feel that you're genuinely interested in what they need, they may be more inclined to hire you.
My best tip is to ask EVERYONE you have a discussion with for a review. Even if they don't hire you but you feel that you had an engaging conversation ask them for a quick review. The more reviews you have the more confidence future contacts will have in hiring you!
My best tip to getting hired is to give the potential client as clear of a picture of your business as possible. Personalize your bids, showcase some of your best photographs of your work, refer to your reviews, add links to your personal sites, etc. The better overall picture that the customer has of your company, the more confidence they will have in hiring you!