CF keeps you logged in. I sometimes have to switch between regions and don't always know where I am #Where am I?
cf target
#Login. This is logging in to the UK region of bluemix. Replace eu-gb with ng to go to the US.
cf login -a https://api.eu-gb.bluemix.net
#List spaces
cf spaces
#Change space
cf target -s OtherSpace
#Change organisation - for when someone adds you to their org usually. This will normally have to be followed by a target of the relevant space.
cf target -o OtherOrg