As anticipated, Ancestry website is offering free access next weekend to
"Our WWI Service, Pension and Medal Records are free from 9th-12th November", ONLY.

As with previous free access periods, there's no "catch" that I can see, no payment is required altho you do need to signup your name & email address. No doubt if you try to access non- WW1 data then they'll ask for payment. For most participants this huge database contains images of the basic but still very informative Medal Index Cards, whereas for some potentially far more detailed Service/Pension Records may exist, but remember 2/3 of the original Records were destroyed during WW2 and the remainder are often incomplete or damaged.
As a "signed-up" user but not subscriber of the Ancestry site for 2 years now, I can reassure you they don't send out pestering emails etc etc, just occasional informative email newsletters sometimes warning of free access such as this. Meanwhile I also benefit from their free search pages and their online family tree builder.

http://search.ancestry.co.uk/search/category.aspx?cat=39

"These records will be available to search for free from 12 midnight GMT on 9 November 2012 until 11:59pm GMT on November 12 2012. To view these records you will need to register for free with Ancestry.co.uk with your name and email address."

------------------------------------------------------------------------------------

"In Flanders"

I'm homesick for my hills again -
My hills again!
To see above the Severn plain,
Unscabbarded against the sky,
The blue high blade of Cotswold lie;
The giant clouds go royally
By jagged Malvern with a train
Of shadows. Where the land is low
Like a huge imprisoning O
I hear a heart that's sound and high,
I hear the heart within me cry:
"I'm homesick for my hills again -
My hills again!
Cotswold or Malvern, sun or rain!
My hills again!"

by F. W. "Will" Harvey (of Hartpury, Minsterworth and Yorkley)

http://www.forum.forest-of-dean.net/index.php?id=7769
http://www.forum.forest-of-dean.net/index.php?id=23492

Contrary to what I was advised by Ancestry and subsequently posted last week, these records are already free to access and have been all day apparently and will remain so until midnight Monday 12th, sorry for my error.

I suggest as a starter try searching the Medal Cards, even just surnames and a local placename might yield surprise results for ancestors you were perhaps unaware about.
I'm sorry but I have no idea whether this Free Access is available to users outside of the UK, altho I would hope it would be for the Commonwealth countries at the very least.

http://www.ancestry.co.uk/free?o_iid=52991&o_lid=52991&o_sch=Outbound

For hints and tips these websites plus hopefully my recent posts on the subject should be helpful.
http://www.nationalarchives.gov.uk/records/medal-index-cards-ww1.htm
NB: the Medal Cards can be freely searched from excellent National Archives site, altho you must then pay to view the card image; apart from name & number the card content is not transcribed on any websites so the detailed content, sometimes extensive!, can only be read direct from the image itself. These cards were invariable filled out by hand, sometimes using unusual symbology and very small handwriting which can be very difficult to decipher. Very occasionally the back of the Card contains info, these images are only availble from Ancestry not TNA.

As well as Ancestry my public Library also offers free access to FindMyPast which I recommend cross searching too. This site carries different military datasets than Ancestry going back much earlier than WW1, so many older men who served in WW1 as Territorials will perhaps be recorded within the Boer War records etc. FMP also sometimes offers extra detail such as Cause of Death wrt men those listed on the various World Wars Rolls of Honour.

Please also see these prior threads for more hints
http://www.forum.forest-of-dean.net/index.php?id=38095
http://www.forum.forest-of-dean.net/index.php?id=38082
http://www.forum.forest-of-dean.net/index.php?mode=thread&id=38992

http://www.bbc.co.uk/history/familyhistory/get_started/archives_01.shtml

A particularly good book available from local Libraries is produced by The National Archives, called "First World War Army Service Records" by William Spencer, one of various related books by them.

Good luck !