Rosie - I just write down the site I got them from - Anc*y or FindMyPast or FreeR. It's then just a question of typing names into a box and hey presto there they are! I think proper genealogists would frown on that though. Should I be more professional?
tl;dr Life's too short to develop an anxiety complex over a source citation.
I basically work from Elizabeth Shown Mills' Evidence Explained but to tell you the truth, I'm not that strict at following the templates. I just adapt stuff so it makes sense to me and add enough that I can find the original source again. I'll usually make a note identifying whether it is just an index/database entry, transcription and/or whether it includes the original image. I also know that 20 years from now, the same sources/repositories/databases etc may no longer exist (such as findmypast or FreeBMD) so it is good to know where & when you found information.
I don't like to make things too difficult for myself so just copy a previous source citation and change the details. As a lot of information comes from the same sources (parish records, census, FreeBMD etc) this makes it pretty easy and just takes seconds. If the site I download from provides citations, I just use theirs and tweak a bit, if I think it is necessary (but usually don't as I'm lazy).

When it comes right down to it, I want to have fun with my research and don't want to be weighed down. However, I know that citations are important to support and validate your research. So I do just enough that it doesn't become a burden and a joykiller.
I'm curious. What does everyone else do? For e.g., Use the templates in your FH program, metadata in digital files, handwritten on back of hardcopies, notebooks or spreadsheets, bits of paper? Do you follow a particular format or just wing it?
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So, for example, for the 1871 UK census I have:
"1871 England Census," database and image, findmypast.com.au (
http://www.findmypast.com.au : accessed 28 February 2016), entry for James Smith (age 45) & family, Bury St Pauls, Bury, Lancashire; citing PRO RG 10/3958, folio 40, p. 5; Bury registration district, Bury subdistrict, household 27.
For FreeBMD:
"England & Wales, FreeBMD Index: 1837 - 1983," database, FreeBMD (
http://www.freebmd.org.uk/cgi/search.pl : accessed 29 February 2016), birth entry for Nancy Diggle; citing September [quarter] 1844, Bury, vol. 21, p. 273.
Online Parish Clerks:
"Baptism records for St Mary the Virgin, Bury, Lancashire, England," transcriptions, Online Parish Clerks for the County of Lancashire (
http://www.lan-opc.org.uk : accessed 28 February 2016), entry for Richard Diggle baptised 4 May 1804; citing "LDS Film 559157, Register: Baptisms 1799-1808, Page 72, Entry 6."
For Family Search or Trove:
I just use their citations & add bits for clarification if necessary.