Looking after strawberries

Good morning gardeners!

More questions from me, I'm afraid..... Please bear with me!

I've been very fortunate in that I found LOADS of strawberries on my allotment plot, and we've been thoroughly enjoying them - best ever strawbs, even though I didn't grow them,  , which makes me want to look after them even more.

Well, I've seen people mulch with straw, and I've taken as much weed as possible from the surface and mulched with non straw mulch (the regular organic stuff). Is the straw better just for keeping the berries off the ground, or does it do more? And, can I pick any straw, for example from the pet shop downstairs, provided it's not covered in chemicals, or do I need special strawberry straw?? In which case, where do I find some? Didn't see any at Wyevale yesterday, and I looked  .  Am I even making sense,    :?:

One last query..... the plants are forming runners, and I read somewhere that you could place vigorous plants' runners over a pot of compost to establish for next year. How can I tell vigorous plants? They're all pretty much quite healthy. Oh, and how do I prune for even more fruiting> Many stalks forming all over the place, they look like spiders!