To download the file "serials.txt" from your remote home dir to the local computer:
scp user@server.com:serials.txt .
To download the remote file "something" using it's full path to your local computer:
scp user@server.com:/path/to/file/something.txt .
Now the tricky part: using the recursive switch (-r) to download a whole folder to your local computer. The issue you may have is that you DO NOT place a trailing forward slash after the directory name. For instance, this command will NOT work (notice the bold forward slash):
scp -r user@server.com:/path/to/directory/ .
This will give you a message saying the server is trying to write to the parent directory. REMOVE the last foward slash on the path and try again. The next command is CORRECT:
scp -r user@server.com:/path/to/directory .
I have been using a period when talking about downloading so far. Reason: this brings the file into the directory you are currently in. If you wish to take the last command and download it to somewhere else, the command would be:
scp -r user@server.com:/path/to/directory /new/local/location/