I just saw this asked (for the billionth time) in a forum. It's a good question-why else would it be asked billions of times?
It's kind of like the Chicken and The Egg question... There really is no answer to it.
Now, here I am assuming that you have done everything else from your business plan to your sales tax ID to your pricing and all that jazz. If you haven't, well... this probably isn't for you-YET.
The question posted was exactly these words: "what is the best way to gain new clients?" No where in there did the poster say anything about themselves or what kind of photographer they were. Considering it is in a portrait forum we can assume that portraits are at least part of their business. Maybe weddings? Maybe sports? Maybe ??? WHY am I harping about those things? Because it's critical to how you will market your business to attract new clients. If you are a wedding photographer you probably won't be targeting pregnant moms.
There are a couple of things you have to do (yep, more!) before you can just gain new clients.
1. Define who YOU are as a photographer. This is part of branding, but it's also critical in marketing. You have to market to clients who will fit you and vice-a-versa.
For this post we'll assume that I am a senior portrait photographer. I want to photograph high school seniors. Pretty broad definition of myself as a photographer? Right?
Now get specific: How many sessions do you want to shoot? What do you want to make in profit (you have to know your average profit margin here)? Do you want them to come to you or do you want to go on location? If you did your business plan thoroughly this is all in there. Make sure you include all of the things that you think are a negative-maybe you don't have a studio and you think that's going to hurt you. Include those things.
2. Define who your client is. Make up a person who is your ideal client. Who are they? Where do they live, play, shop? What do they value? What brands are they buying, wearing and using? How much money are they going to spend with you? WHERE are you going to see this person? What do they read? Watch? Who-what-when-where-why-how. How will you fit into the things they value? How will they NEED to have YOU and only you?
Now that you know those two things you can easily see ways to get in front of that ideal client. You can also find ways to make your negatives into a positive. You don't have a studio? GREAT! You go to the client's home! You want only the clients who are going to spend $1000? GREAT! You are EXCLUSIVE and only the select few will have the privilege of having their senior portraits taken by you! You see where I am going here? By defining everything about you and your client you can figure out how to market to them and where.