When I was starting in commercial product photography (tabletop) I would go out and purchase products myself and then shoot them how I would envision a campaign to be. Once I knew there was a cosmetics company who was needing a photographer to shoot a new lotion campaign. So I bought a different brand of lotion products and went to town with them. I created a whole visual campaign of images on my own that I added to a portfolio and presented.
This is certainly a good idea, and one that would easily work. I would suggest partnering with a local mom and pop store and give a few prints in exchange for shooting the various products. Exchange a family portrait and you may get plenty of products to shoot. If you play it right with the business owner, you could parlay it to a few local businesses.
You could also work out a deal to sell prints in the same store. Gives them a zero loss opportunity to make a few extra dollars.

When I moved over to commercial campaign photography (people and products) I spent hours at the local library going through magazines and studying what current people and product ads looked like. I then went back and created several "mock" shoots for various industries (Computer, corporate, F&B) Those went into my book and from there I was able to book paid shoots. Again, I was working on my business and investing in myself not anyone else's potentially empty promises.
Fantastic advice and a great way to accomplish this goal.

I created a book by bribing my close married friends to put back on those wedding dresses and renting a tux's for them and going out and shooting them in fake set-ups. Same thing for fashion photography. Those books got me jobs with some studios and agencies while maintaining my personal integrity and beliefs.
Weddings are tough and I would suggest that anyone interested in wedding photography begin with being a 2nd shooter. I do love the "staged" idea and it would certainly fill a book fast.

And with my current industry I actually did what few pro photographers would ever consider doing (no it was not offering free shoots either) I went back to being an assistant.
Again this is a superb idea, with very little chance of a downside.

As far a photo credit goes in magazines, ect.... It really does not mean that much, to clients at least (to you as a photographer in personal satisfaction, sure).
This has worked well for me, although it should be noted that I do product shots. In general I will agree that in and of itself a tear sheet won't get you much work, but depending on what you do and the connections that can be worked it can be a valuable tool.

Be careful of those "trade" situations.
100% agree here. Working the trade to your advantage requires some business understanding. I am a huge fan of exchanging services for goods or services that benefit both parties. I would certainly shoot the plumbers family portrait in exchange for free installation of my jacuzzi.

With all of this back and forth, I hope that the readers of this thread have picked up one or two good things. Spectrumphoto has offered some of the best written and well thought out explanations and alternatives that I have seen in an online forum in quite some time.

When you are considering a free shoot, ask yourself why. There are times where I will shoot for free, and have no issues with it, but on these occasions it is because I choose to, not because I have to.
If there comes an opportunity to change careers and pursue, say shooting a fashion show. Something definitely outside of my normal day to day shooting area.

I would find some local fashion show. (happens in California quite regularly) and meet with the organizer and discuss what it would take for me to shoot that show. I would not demand to be paid, or ask for other special deals. I would be willing to give more in exchange for the opportunity. I would ask for more than just the ability to shoot the images. A better location or maybe backstage. I would show the organizer my previous work and shots that were kind of similar to what I hope to capture. If my work turned out good, I would add it to my book and look for larger fashion shows. Working my way up to the chance to shoot with local designers for small paychecks or some form of payment. Once you have your foot in the door, working you way up the ladder is far easier.

There have been quite a few threads where a photographer is out taking fun shots and someone sees the image and wants to buy it or use it.
Lord knows that I love the fun shots, and take as many as my free time allows. If I were a weekend shooter with a real job, and I wanted to maybe see where the photography business could take me, or maybe just figure out a way to feed the habit, I would be willing to give a tad more.

Let's say that I shoot a (insert an image here) and some event organizer or newspaper or whatever contacts me wanting to use the image.
If the image is not award winning or a once in a lifetime shot, I would figure out what the image would be worth. There are plenty of online and print calculators for this type of stock shot.
You could quote that price and be willing to hear the word NO or be ready to walk away if the price is not met. Easy enough and there is nothing wrong with that.
You could also figure out what the person could do for you. Can they get you into an event or situation that could lend itself to a position to get more shots, or maybe to a place where you could attempt to sell other shots. Again there is nothing wrong with this approach.
You really need to figure out what your image is worth. Not everyone can charge hundreds or thousands of dollars for an image, but it is worth something or they would not be asking for permission to use it.