Some of the useful info when working with ADB on phone

For remounting the system partition as RW on Galaxy SL, (need to be super user)

# mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system

For mounting back to RO

# mount -o ro,remount -t yaffs2 /dev/block/mtdblock3 /system

Basic ADB commands

# adb push <local_path> <remote_path>

# adb pull <remote_path> <local_path>

# adb install <path_to_apk>

If you have not installed the cp command may not work, the work around would be 

# cat [source_file] > [destination_file]

The command binaries would be located at this location, /system/bin/ And if you had installed busybox, in /system/xbin/ then first the above path is looked for command, and later the below path.

The /system partition has limited memory, so if you try installing too many applications here, then you may run out of space, and its a better idea to delete many of the unwanted bloat applications from there. I have deleted the following apps and they do not be of much use for me. May be if its not useful for you, you can delete them as well. And you can also delete any other apps which are of no use for you.

1. Samsung Apps [They are meant for Bada, and of no use in Android! wonder why its added here!]
2. BuddiesNow.apk/odex
3. thinkdroid.apk/odex [ThinkFree Office - I have installed Polaris Office instead of this, which is much better]
4. Day.apk/odex
5. DualClock.apk/odex
6. SamsungWidget_Calenderclock.apk/odex
7. SamsungWidget_Feedandupdate.apk/odex
8. SamsungWidget_stockclock.apk/odex
9. SamsungWidget_Weatherclock.apk/odex

All the best, and keep a backup of the file before altering or deleting any file inside /system partition, so that you can restore if something goes wrong, and I am not responsible for any thing if at all it goes wrong :)
Some useful tips and tricks about galaxy S/SL can be found here, its quite long, but when free go through.