iTunes Smart Playlists are a great way to auto-populate playlists that you listen to often. I listen to alot of podcasts, so I created a "programs" playlist that is populated by podcasts I subscribe to, as they become available. Of course, Smart Playlists are not just for podcasts, but I'll use podcasts for illustration's sake in this how-to.
As neat as they are, Smart Playlists do have one major limitation, there is no way to mix boolean "AND" and "OR" expressions. To illustrate, let's say I wanted to create a Smart Playlist containing the "Marketplace" and/or "Planet Money" podcast, but only ones added in the last two days (new episodes). Simple concept, but it's actually not possible with a single Smart Playlist. See below:
If I chose the match "all" following rules option, I would get a list with no podcasts on it (because there are no podcasts that are labeled both "Marketplace" and "Planet Money"). If I choose the "any" matching method, I would get the podcasts I desire, but I'd also get every other podcast that's arrived in the last two days (because of the third rule). Not quite what I'm looking for.
The good news is that there is a solution. One of the rules you can select basically says "...and is on the playlist x". That's the key! So, we can create a playlist-of-playlists, or nest "member" playlists, containing rules specific to each podcast, to get what we want on a single playlist. This helps us achieve the mixing of boolean AND and OR expressions that a straight Smart Playlist can't do.
Step 1: Create a new playlist folder in iTunes. We'll call it "nested" for purposes of illustration. Creating a folder is not absolutely necessary, but since these playlists aren't going to be directly accessed, I like to keep them contained for housekeeping reasons (you can collapse it to save space).
Step 2: Create individual member Smart Playlists within the "nested" folder. Each playlist should contain the specific rules you want for each individual podcast you want on your master playlist. For example, one playlist for new "Marketplace" episodes within the last two days, and another for new "Planet Money" episodes within the last two days. (Note: There are a variety of ways to match a podcast - by Album is what I use because it's consistent). Be sure to match by "all following rules" on your member playlist. Also, if you're making a playlist of podcasts, be sure to add a rule, "Play Count is 0" to exclude podcasts you've already listened to. Don't do this if your playlist is of music.
Step 3: Create a "master" Smart Playlist that will contain our nested member playlists. First, click away from the "nested" folder (click on Library->Music) so we can create a top-level iTunes Smart Playlist (we don't want this one inside the "nested" folder). In the Smart Playlist dialog box, make sure to select "any" as the matching method (very important), and add one rule for each member playlist you created. In this example the first rule is "Playlist contains Marketplace" and second is "Playlist is NPR: Planet Money".
When you click "OK" you can name the playlist whatever you wish. I'll call it "Awesome Business Podcasts".
And voila! There's our incredible new complex-rules Smart Playlist. New "Marketplace" or "Planet Money" episodes will automatically arrive and old or previously-listened shows will automatically drop off.
There's about a bazillion different things you can do with Smart Playlists, and even more when you create complex Smart Playlists like we did above.
But one problem I ran into even with these "smarter" Smart Playlists is how to handle when, for example, I want to make a "finance" playlist all new Planet Money and Marketplace episodes (like the example above), but also a handful of select finance programs (podcasted or not) from the past.
Easy enough! Just create a nested member playlist called "Manually-Managed" (note: this is a regular playlist, not a smart playlist) and added my desired past episodes to that. I then include that "Manually-Managed" playlist on my master playlist. Here's a snot of my master podcast playlist, along with the nested member playlists that make it up:
You can add unlimited nested "member" playlists to a "master" playlist. I've heard some grumbling that it sucks up computer resources to do this, but that is not my experience.
One neat thing to note about Smart Playlists is that you can manually re-order them. So if I wanted to listen to Marketplace first, I just drag it to the top. If you are going to use this playlist on an iPod or iPhone, be sure to set it to sync whenever you plug it back into the computer. That way it will update your library with the play count (and therefore update the Smart Playlist).
Here are some links detailing other great Smart Playlists you can try: