Being a performing musician is a rewarding and exciting experience.  Many times, especially when first starting out, you'll need to  play some free shows in order to build a fan base, sharpen your performance skills, and become established in your area.  Normally venues will allow you to use a tip jar as a means for compensation at these types of performances.  It's important to maximize this opportunity to earn some money by using the following techniques.

Choose the Right Container - Performers in the past have used everything from an open guitar case, a hat, or an empty coffee tin as a tip jar.  Anything will work, and it's fun to get creative, but the most successful tip jar is one where patrons can easily see the money that's already in there.  This will ensure that there is no confusion as to exactly where their money should go.  Glass jars are great, as well as large open containers, like the aforementioned guitar case.  Any confusion as to where entertained patrons can toss their cash, and they will quickly close their wallets and move on.

Seed the Tip Jar with a Little Cash - Related to the last point, you'll want to make sure that when you start your show, you throw a couple dollars of your own into the jar.  This will make it clear what the purpose of your tip jar is.  It will also provide a bit of social proof, if people feel like others have already felt the need to tip you, they are more likely to follow suit.

Place the Tip Jar in a High Traffic Area - Location of the tip jar is very important.  You want to make sure it's as easy as possible for patrons to give you money.  Try to find a spot near the cash register, the door, or somewhere in between where the majority of customers will pass.  Making them go out of their way to find the tip jar means you'll loose out on potential tips.  It's also a good idea to keep the tip jar close to you so people associate it with you.  If that's not possible, make sure to label it in such a way that it is understood that the money put inside goes to the performer.  

Mention the Tip Jar Frequently - Even the best positioned tip jar can be overlooked by busy, distracted, or less observant folks.  That's why it's important to mention its existence and location every now and then during your performance.  Speak directly to the people who have appeared most engaged with your show and say something like, "If you've been diggin' the tunes, help support local music by throwing a couple bucks in the tip jar over there".  It doesn't have to be a complex sales pitch or anything, but try to equate the audience enjoyment with your compensation, this will make sense to people and they'll be more likely to donate.

The Pass-the-Hat Approach - The ultimate cash generator is the pass-the-hat technique.  This requires that you have a friend with you who will walk the tip jar around the audience while you're playing.  This ensures that all audience members know about the existence of the tip jar.  It also places a little pressure on them to make a snap decision at the moment your friend brings the tip jar to them.  If they had the slightest inclination to give you money, they will do it at this time, without having the chance to talk themselves out of it later.  Be careful not to overdo this.  Keep it to once or twice per show, depending on the length and number of people present.  You don't want to shove a tip jar in the same persons face multiple times or it will feel like you're doing this only for the money, and we all know that's not true!

These tips, along with great songwriting and performance skills, will help you get the most money possible from your free gigs!