"it is basically my livelihood"
How can it be your livelihood if you don't have clients?
"HOW DO I START MY CLIENT LIST AS A PHOTOGRAPHER?"
You start a photography business like you would any other kind of business you build a business plan and secure some start up capital.
That being said, the VERY FIRST THING you need to do is sit down, look at your portfolio and ask yourself "Would anyone pay me to shoot these photos"? Then, if your answer is yes, submit your photos for a critique by professional photographers and see what THEY have to say. Listen to ALL THE COMMENTS, EVEN THE NEGATIVE ONES!
This is important because YOU may think you are good, your friends and family may think you are good but you are all biased ... you have an emotional attachment.
So, let's say your work is decent and you can consistently produce that quality of work under various, less than ideal conditions. Then you need to start by building a business plan.
One of the things you'll do in that business plan, is work up a MARKETING PLAN and a BUDGET for that marketing as will a metrics to use to gauge the effectiveness of that marketing. Each type of photography will require it;s own marketing approach ... Going to a wedding show to market pet photography isn't going to work all that well for example.
Be aware that marketing WILL COST YOU MONEY ... AND LOTS OF IT. Business cards, hand out like Flat cards, printing a nice layflat book as a portfolio (or 2 or 3 ... you want them built for specific market segments), attending trade shows like bridal fairs ...
Look into the cost of these approaches, look at your available marketing budget, find the one that has the best chance of getting oyu a good RoI (Return on Investment), TRACK REVENUE vs MARKETING DOLLARS to gauge what your RoI is.
"do free work in the hopes they will call back one day with real orders"
HELL NO! There are literally hundreds of thousands of peoiple just like you looking ot break into photography ... if you give your work for free you devalue photography and your "client" (if we can call them that) will get accustomed to not paying for photography. Why would they pay you when they can get another sucker to do the work for free ... plenty of other suckers out there.
People have to stop doing free work.
"or make fliers & pin them wherever possible?"
Not very effective, you have to narrow your focus and really maximise your marketing dollars. Wedidng shows are a good place to meet clients ... of course a booth at a wedding show can easily cost your 2000$ per show when you factor in marketing materials (flat cards, business cards ...) ... flyers pinned outside? Useless!
Pay for direct marketing services, attend trade shows (bridal shows, pet shows ...), market with other related professionals ... it's going to be hard work and it will take time but eventually (if you are good enough and persist) it will pay off.