hi There,i Will Show You The Command block Codes...

type /give 137 -It Will Gives you command block

Now The Main Rule In Command block is to Have a (/)slash... Ok Good Here are the Commands that you are waiting for:

1./give @....... It Will gives A Item You Selected..
2./tp @ (x) (y) (z).........Warp or Teleports Player to the selected area....
3./say @ ......... The Player Selected Will get the message....
4./tell @ ......... private message to the player selected
5./xp @ ............. A Player Selected Will Reseaved a Experience Points
6./effect @ ...... A Player Selected Will Reseaved a Effect..
7.gamerule ...... A gamerule Will Updated..
8.gamemode @ ...... Gamemode will Change To the player selected.
9.weather ... weather will change
10.clear @ ...... a player selected will clear his inventory.

COMMANDS:
@p------- Target Selected player
@a------- Target All Players
@r--------Target Random Player

GAMEMODE:

adventure
survival
creative

WEATHER COMMANDS:
clear----Clear Weather
rainy----Change to Rainy
thunder--A Rainy With thunder.