The only way to shrink the size of the file is to shrink the size of the file.

If your file is growing too large, you have a couple of choices. First, take more frequently log backups. If you're mirroring, increase the frequency of the log transmission. Second, reduce the size or number of transactions by adjusting your code. That one is frequently extremely difficult, but it is sometimes possible.

That's it. We really have very few options in managing log file size.