Find a website which provides information on transactions in recent blocks.
https://bitcoinfees.21.co/
http://bitcointicker.co/networkstats/ (click Fee - btc/kB - within n blocks)
Then choose a fee based on the size of your transaction and how soon you would like it to confirm.
Simple.
Thanks for the reply Holliday.
I was using the first site you mentioned when calculating my fees, but I'm not sure MultiBit is labelled correctly.
It's says select a TX fee per byte, which I did, but it doesn't show me how many bytes the TX is going to be?
Then when I view the TX on the BC it seems to have used my "fee per byte" as the total fee, but, and this is the weird part, not always. The one that took 36hrs (TX #2 above) said the fee was a total of $11.34 so what's going on there?
Maybe I should just jog on this wallet once and for all :/
Well, unfortunately I can't help you with MultiBit as I've never used that specific wallet. Perhaps a MultiBit user will see your thread here and give you the info you are looking for, or maybe you'll have better luck asking in the MultiBit sub-forum.
https://bitcointalk.org/index.php?board=99.0
Good luck!