I went along to a ukulele session today (and before today didn't even have any idea how to spell ukulele!).  
It was great fun.  Six of us sat around in a friend's living room with our ukuleles and sang along to our strumming (with varying degrees of competency).  


First to learn was how to actually hold the ukulele.  Some people held it horizontal but I found it easier to hold more upright. The instrument which I borrowed had a strap which helped to balance the weight.


We played several pieces and the chords were marked above the words, with a diagram at the side.  

To start with I just sang along and played the chord of C whenever it appeared - the easiest one to play.  Then added another chord when able to.  


One piece only had three chords, whereas others had more like six or eight.  So that song involved more singing than strumming.

My class was with Derby U3A (http://u3asites.org.uk/code/u3asite.php?site=158) and the leader, Duncan, was very patient and encouraging, so I'm looking forward to learning more.  It's fun to play along and sing with others.

The strings are keyed (l-r) G-C-E-A  and this is a way to tune the ukulele without a keyboard or similar help: 
http://www.get-tuned.com/online_ukulele_tuner.php

The most common ukulele chords are C, D, F and G, see: http://ukulelehunt.com/2011/09/07/most-common-ukulele-chords/

Strumming tips for beginners:https://ukuguides.com/tips/10-ukulele-tips-for-beginners/
and
https://www.youtube.com/watch?v=6eqH_jZp1Ow
and also:
http://www.ukuleletricks.com/5-effective-strumming-patterns-for-beginners/

Top 99 songs is a good site.  The chords are given at the top of each song and as you move down the page to go through the song the chords stay at the top of the screen all the time - a very good reminder for those 'blank' moments:
https://ukutabs.com/top-tabs/99-most-popular-ukulele-songs/all-time/

'Something' by the Beatles: https://www.youtube.com/watch?v=OK6QXMZFnPU

And here are a few more interesting sites about playing the ukulele:
http://www.wikihow.com/Play-the-Ukulele
http://ukuleleunderground.com/lessons/learn-to-play-the-ukulele-in-5-minutes/
http://willgrovewhite.com/learning-to-play-the-ukulele-lesson-one/
https://www.youtube.com/watch?v=78nr8QMaUbI
http://ukuchords.com/files/ukuchords_complete_chords_chart_180.pdf