Once you’ve decided what costume to build (or if you need some help deciding!), you should seek out the proper Legion Detachment for it. Each costume in the 501st Legion falls under one of fifteen Detachments. Detachments are how we organize costumers so that they can reach people with the same needs as others who share their outfit. For example, Sandtroopers belong to the Mos Eisley Police Department (MEPD); the Armored Cavalry Detachment covers AT-AT and AT-ST Drivers and Armor Assault Commanders (like General Veers); Biker Scouts have a headquarters with the 501st Pathfinders; and so on.
Joining the Detachment of the uniform you are aiming for is a great way to get straight to the experts on your costume. Join their forums, read old threads, introduce yourself and let everyone know why you’re interested in joining up, send a private message (PM) to the Detachment Leader asking for advice, and start asking questions! By researching your costume on a Detachment site, and by asking questions there, you will hit a broad base of people who are keenly knowledgeable about a particular costume.
And unlike the 501st.com Legion Message Boards, which are members-only, the message boards on Detachment sites are open to anyone in the public who would like to register and join in the conversation.
Note, however, that most (if not all) Detachments have rules on their forums about posting “Want To Buy” (WTB) threads. Usually these are immediately deleted for the legal reasons we discussed above. So heading to a Detachment gets you into the company of people who can help you, but you still have to overcome a few technical hurdles.
A full list of Detachments, the costumes that they cover, and links to their websites can be found on the main Legion site, here: 501st.com/resources.php