Problems with intonation and clarity seem to find their way into everything I play. Using a tape recorder can help iron out some of the larger problems, but pinpointing the smaller ones can be difficult.
Enter Audacity, and its possibilities for slowing down recordings (you can see the playback slider above). By listening to a playback at half speed, it is easy for me to notice exactly which pitches are out of tune, which shifts are not accurate, and which string crossings are not clean. It is particularly useful in fast passages, but it works with slow ones as well. I can circle the culprit notes and intervals in my music, correct the problems by practicing carefully, and make a comparison recording of the result.
It works like a magnifying glass. Once those pesky little problems are magnified, they are much easier to see, hear, and solve. Focusing on the right stuff saves a great deal of time and energy, making practice time far more productive.