I'm just going to say this now and I wont say it again, although i know in this economic climate it isn't a time to just go out and buy new things. But your knives its makes prepping; even at home, chopping some vegetables much more difficult and time consuming if you don't have sharp knives. I have a selection of knives from ones that are well known brand from Global to Wushtoff to a generic brand that was on offer in a Supermarket. Yes the knives are made of different materials but if they aren't sharp they are pretty much useless!
To sharpen your knives I would tell you to buy a tone if you are in dire need other than that a steel should do just fine. I would sharpen my knives at least once a week depending on the usage, it also helps to give your knives a longer shelf life - if your cutting with a blunt knife you can risk chipping it and if its chipped badly you may not be able to get it back. If you injure yourself with a blunt knife it can be much more serious than with a sharp knife, so to be safe - sharpen them!
If I really need them sharpened I will head to my local butchers and leave them in to be sharpened, and as they told me "if it doesn't cost us anything, it won't cost you anything". But I don't know if everywhere offers the free service. That's it I said and I won't say it again.