Make:

If you're a heavy iTunes and iPhoto user, you will probably quickly overflow the limited storage in the iPhone. You could dedicate a day of curatorial work to sifting through your photos and music to pick the ones to put on your phone, but if you want a quick and dirty solution, try creating a Smart Playlist and Smart Album that favor recent music and photos.

If you only want to hear music on your iPhone, create a Smart Playlist with conditions like this one:

Match

All the following rules

Last Played

is in the last 120 days

Play Count

is greater than 2

Genre

is not Spoken Word

Genre

is not Audiobooks

Genre

is not Podcast

Limit to

250 items, selected by random

(Since Podcasts have their own tab in iTunes, they are probably synced separately from music anyhow, but it can't hurt to have them in the exclusion list.)

If you buy a lot of music in the music store, you can also force some purchased music onto the iPhone with a second Smart Playlist:

Match

All the following rules

Playlist

is Purchased

Play Count

is greater than 2

Genre

is not Spoken Word

Genre

is not Audiobooks

Genre

is not Podcast

Limit to

250 items, selected by random

If you're using iPhoto, you can create a simple Smart Album that specifies "Date is in the last 90 days" and you'll get all your recent photos. If you use more than one camera, you can add one or more additional conditions: "Camera model is not...", and put your low-quality cameras in there, such as your cameraphone. That way, you'll be more likely to get your most polished photos in the mix.

Once you've done that, go into iTunes, click on your iPhone, and then go to the Music tab. Tell it to Sync Music, but only the "Selected Playlists." Pick the playlist(s) you just created. Do the same on the Photos tab, and tell it to sync only the album you just created. You'll probably need to tweak the number of items in your playlists, and the number of days in your playlist and album to get a good balance of photos, music, and free space.