I thought I would post a quick guide on macro creation as this is something people may not have done before or understand.
Step 1 - Access Macros Screen
Hit Escape to see the game menu and click the "Macros" button
Step 2 - Create a New Macro
Click the "New" but and a new little window will appear
Step 3 - Name and Pick and Icon
type in a name that is meaningful for you and select an icon. If you pick the "?" the icon will be the default icon for the first spell\ability\object relevant in the macro.
Click "Okay" once that's done.
Step 4 - Create Your Macro
now this is the hard part, you can either work on your own or download one from websites.
Breaking down the example here;
#showtooltip will mean when you mouseover the macro it will should be Tooltip for the relevant spell. If you put a spell name in it will show that tip, if not will show the first spell\ability etc.
In this macro it will trigger the use of your trinkets if they are available and then cast Arcane Shot.
Step 5 - Add it to your hotbar
Easy peasy, just drag and drop the macro icon to the toolbar of choice, this can then be triggered via your hotkeys :)
Wowwiki has a vast range of macros that are both general and class specific so have a read of that :)