adb –help

-d                            - directs command to the only connected USB device
                                returns an error if more than one USB device is present.
-e                            - directs command to the only running emulator.
                                returns an error if more than one emulator is running.
-s <specific device>          - directs command to the device or emulator with the given
                                serial number or qualifier. Overrides ANDROID_SERIAL
                                environment variable.
-p <product name or path>     - simple product name like 'sooner', or
                                a relative/absolute path to a product
                                out directory like 'out/target/product/sooner'.
                                If -p is not specified, the ANDROID_PRODUCT_OUT
                                environment variable is used, which must
                                be an absolute path.
devices [-l]                  - list all connected devices
                                ('-l' will also list device qualifiers)
connect <host>[:<port>]       - connect to a device via TCP/IP
                                Port 5555 is used by default if no port number is specified.
disconnect [<host>[:<port>]]  - disconnect from a TCP/IP device.
                                Port 5555 is used by default if no port number is specified.
                                Using this command with no additional arguments
                                will disconnect from all connected TCP/IP devices.

device commands:

 adb push <local> <remote>    - copy file/dir to device
 adb pull <remote> [<local>]  - copy file/dir from device
 adb sync [ <directory> ]     - copy host->device only if changed
                                (-l means list but don't copy)
                                (see 'adb help all')
 adb shell                    - run remote shell interactively
 adb shell <command>          - run remote shell command
 adb emu <command>            - run emulator console command
 adb logcat [ <filter-spec> ] - View device log
 adb forward <local> <remote> - forward socket connections
                                forward specs are one of: 
                                  tcp:<port>
                                  localabstract:<unix domain socket name>
                                  localreserved:<unix domain socket name>
                                  localfilesystem:<unix domain socket name>
                                  dev:<character device name>
                                  jdwp:<process pid> (remote only)
 adb jdwp                     - list PIDs of processes hosting a JDWP transport
 adb install [-l] [-r] [-s] [--algo <algorithm name> --key <hex-encoded key> --iv <hex-encoded iv>] <file>
                              - push this package file to the device and install it
                                ('-l' means forward-lock the app)
                                ('-r' means reinstall the app, keeping its data)
                                ('-s' means install on SD card instead of internal storage)
                                ('--algo', '--key', and '--iv' mean the file is encrypted already)
 adb uninstall [-k] <package> - remove this app package from the device
                                ('-k' means keep the data and cache directories)
 adb bugreport                - return all information from the device
                                that should be included in a bug report.
 adb backup [-f <file>] [-apk|-noapk] [-shared|-noshared] [-all] [-system|-nosystem] [<packages...>]
                              - write an archive of the device's data to <file>.
                                If no -f option is supplied then the data is written
                                to "backup.ab" in the current directory.
                                (-apk|-noapk enable/disable backup of the .apks themselves
                                   in the archive; the default is noapk.)
                                (-shared|-noshared enable/disable backup of the device's
                                   shared storage / SD card contents; the default is noshared.)
                                (-all means to back up all installed applications)
                                (-system|-nosystem toggles whether -all automatically includes
                                   system applications; the default is to include system apps)
                                (<packages...> is the list of applications to be backed up.  If
                                   the -all or -shared flags are passed, then the package
                                   list is optional.  Applications explicitly given on the
                                   command line will be included even if -nosystem would
                                   ordinarily cause them to be omitted.)
 adb restore <file>           - restore device contents from the <file> backup archive
 adb help                     - show this help message
 adb version                  - show version num

scripting:

 adb wait-for-device          - block until device is online
 adb start-server             - ensure that there is a server running
 adb kill-server              - kill the server if it is running
 adb get-state                - prints: offline | bootloader | device
 adb get-serialno             - prints: <serial-number>
 adb get-devpath              - prints: <device-path>
 adb status-window            - continuously print device status for a specified device
 adb remount                  - remounts the /system partition on the device read-write
 adb reboot [bootloader|recovery] - reboots the device, optionally into the bootloader or recovery program
 adb reboot-bootloader        - reboots the device into the bootloader
 adb root                     - restarts the adbd daemon with root permissions
 adb usb                      - restarts the adbd daemon listening on USB
 adb tcpip <port>             - restarts the adbd daemon listening on TCP on the specified port

networking:

 adb ppp <tty> [parameters]   - Run PPP over USB.
Note: you should not automatically start a PPP connection.
<tty> refers to the tty for PPP stream. Eg. dev:/dev/omap_csmi_tty1
[parameters] - Eg. defaultroute debug dump local notty usepeerdns

adb sync notes: adb sync [ <directory> ]

 <localdir> can be interpreted in several ways:
 - If <directory> is not specified, both /system and /data partitions will be updated.
 - If it is "system" or "data", only the corresponding partition
   is updated.

environmental variables:

 ADB_TRACE                    - Print debug information. A comma separated list of the following values
                                1 or all, adb, sockets, packets, rwx, usb, sync, sysdeps, transport, jdwp
 ANDROID_SERIAL               - The serial number to connect to. -s takes priority over this if given.
 ANDROID_LOG_TAGS             - When used with the logcat option, only these debug tags are printed.

Content of this page is based on informations from wiki.cyanogenmod.org, under CC BY-SA 3.0 licence.