Find files by name:

# find /etc -name ntp*    

  /etc/ntp
  /etc/ntp/ntp.keys
  /etc/ntp.conf

Find files modified in the last 3 days:

# find /etc -mtime -3

  /etc
  /etc/cron.d
  /etc/cron.d/FIFO
  /etc/dfs
  /etc/dfs/dfstab
  /etc/dfs/sharetab

Find files by inode - Good for finding hard-linked files:

# ls -li /etc/init.d/volmgt
  1456 -rwxr--r--   6 root     sys          391 Mar 18  2004 /etc/init.d/volmgt


# find /etc -inum 1456

  /etc/init.d/volmgt
  /etc/rc0.d/K05volmgt
  /etc/rc1.d/K05volmgt
  /etc/rc2.d/K05volmgt
  /etc/rc3.d/S81volmgt
  /etc/rcS.d/K05volmgt

Find files containing certain text:

# find /etc -type f -exec grep apache {} +

Find files by size:

# find /export/home -size +100000000c

  /export/home/scott/sol-9/sol-9-905hw-ga-sparc-v1.iso
  /export/home/scott/sol-9/sol-9-905hw-ga-sparc-v2.iso