Hey, everyone. I have a potential client at the moment to whom I must explain that I won't do any work without a down payment beforehand. How can I politely tell him this?
 
Better yet, maybe we could make a list of equivalent statements here that would be a okay, non-rude/forceful ways to explain things to a client?

You tell them straight.... Best in a middle of a friendly conversation. They should respect you for that, if they don't they probably aren't worth working with anyway.

I generally start with a phrase beginning with 'well I have to put on my business cap on here'...

Don't lack confidence when you say this, humans can detect a deer in the lights several miles away.

Remember they want something and so do you. Acknowledge it or feel awkward..

Yep, agreed. Slide it into a friendly conversation. Be nonchalant, yet confident when you say it. If they go away, the business was not going to be worth the headache.

I certainly don't NEED the business with this client. What kind of more casual conversation do you guys think could be appropriate? It's a small game design team (really quite small). Maybe that's my point of conversation, haha!

Put a sticker on your forehead?

"ok...so to get started, I require a down payment of $__.  Did you want to go ahead and pay that now?"
 
I would assume all conversation to be of the friendly nature.  You can't be this shy over this kind of stuff..., because what's going to happen when the bass player says he's not going out to pick up the pizza anymore?

It sort of depends on how much you are talking about. Have you got any idea at all what this job is worth?  If I was transferring a tape to CD or something like that and the cost was going to be $250 or even $500 I doubt I would ask for a down payment.
 
Once the size of the job gets to say $1000 then I just say to the client a down payment is needed to get started.  (I often ask for a third up front, a third about half way through and the final third on completion. If a job spans several months then we work out a payment plan. It is very important to have money coming in on a regular basis over a longer job)
 
How much do you think the job is worth to you? What is their budget?  Are they the same?  Probably not.
 
Money is very important and you need to get that sorted out first!!  You might think the job is worth $2000 and they might think the job will cost $200.   Don't get all the way to the end to find that out please.  Find out before you start.  Then you might save a whole bunch of time.
 
If you cannot handle the money side of the business then you are not going to make it producing music professionally and getting paid to do so.  Professional music production is very much a business thing too. Musicians are notorious for being terrible in this area.  Learn about it!
 
Clients actually like it when you are confident and direct about money.  It instills confidence in them in you.

omg people get paid for this??

... I don't.

I learned very quickly that you NEVER flinch when giving someone a price. As soon as they detect fear or apprehension in your voice, they have the upper hand. Tell them straight with confidence as if it's the most normal, reasonable thing in the world.

Many years ago I worked the Christmas markets in Manhattan selling overpriced gel candles. One year we had a lovely girl working with us but she would become positively apologetic when giving prices to customers. She would wince visibly and stammer her way through an explanation until boom, she'd talked herself out of a sale. It was funny to watch (especially when she turned bright red when mentioning the sales tax) but she was terrible at selling.

A few years ago I introduced a service agreement for my current business which outlines a penalty fee if clients cancel appointments without adequate notice. It's pretty standard, but in the beginning I would tie myself in knots trying to explain and justify it to clients, and as soon as they detected this weakness they would pounce and try and argue against it. Now I just lay it on the line as if it were part of the constitution and they don't even question it. Confidence will get you everywhere.