I have a request from all users to default the Subject of new Cases to have some verbiage and then display text from a field on the related Contact. IE: Subject = Site ID: XXXXXX (X being the data from the Contact_Site_ID__c field. Can this be done someone without custom apex code? We do not have a developer on the team.
You can create a field update on the subject field from workflow rule that fires 'when a record is created'.
If want the information to populate when on the new/edit screen you will need to create your own edit/new case buttons. There are multiple examples on how do to this on this site and on salesforce blogs.
Another method you could look at is setting up a Publisher Action. Using Publisher Actions, you can default fields and it's more supported than the URL hack method. However, where to put this Action can be a problem. You could stick it on the Account, Contact, any other objects that a Case should be generated from, but you'll have to make a duplicate Action for each of these objects (you'll have to duplicate in the method below as well). Or you could make a Global Action. Here's a decent article on creating Actions.
PepeFloyd linked to the post on URL hacking. As the answers and comments on that post suggest it's not ideal or supported and does have some caveats (mobile, standard buttons), but it will probably work fine.
cas14 is subject
Keep in mind if you want special characters or spaces in the text you will need to URL Encode them.
- %2F is "/"
- %20 is "blankspace"