When the last time you got on a bus, you ended up asking for a child ticket, despite being at least 5 years too old for one (goodness only knows how I still get away with it!). But in reality, you can't afford bus tickets any more, so you cycle everywhere (on a second hand bike donated by a family member), can't afford the repairs on it, but are seriously considering doing 175 miles on a bike to save the train fare. A car seems an unimaginable luxury. And then a family member asks why you don't get a taxi when you have to be somewhere so early that the sun's not come up and the buses haven't started running 
When you have holes in your shoes, in winter, bigger than a 2p piece, and the only reason you get a new pair is because your mum takes pity on you.
When you go to the supermarket with a friend, and the friend looks seriously confused as to why you are so excited to find a well-stocked reduced section (not really a truly skint thing, more of a why-don't-you-understand thing) . . . friend in question also doesn't understand why I go to ethnic supermarkets and always buy value ranges.
When all of your possessions, with the exception of pots and pans, very, very easily fit into a room that is 5m x 3m . . . and the furniture belongs to the landlord, not you. At least in part because you've sold anything that will sell on eBay / Amazon - the other part being that capital purchases aren't really catered for in the budget.
When the only way you can contemplate "new" clothes is by buying the cheap ones, second hand, off of eBay, usually sniping at the last moment - invariably for 99p.
This thread does make me realise that I'm luckier than many though - at least I'm not at the stage of reusing teabags. I'm sorry I don't have anything to offer others though :(
Have you all seen www.moneysavingexpert.com though? It's been incredibly useful to me, it's run by a moderately well-known freelance journalist, and is totally free to use.