Configure Squid so that it doesn't create any log files, except for the swap.state file(s).
Write a simple Perl or awk script to calculate your cache hit ratio from access.log.
How does an "access denied" response appear in the access.log?
Does store.log have the same number of, more, or fewer, entries than access.log?
Take a file number from store.log and find the corresponding file in the disk cache. Examine the file and make sure you've found the correct response.
Develop and implement a policy for archiving old cache log files. Consider where and how they will be stored, for how long, and who has permission to access them.