[Benandbill]

...
Our friend said when the buds come you have to nip them off or something, but to me this seems silly as the flowers won't come then will they?  Also she told us to pinch off the spindly bits at the end of the shoots.  Well they're the bits the plant uses to cling and climb, but it's already clinging to its sticks for all it's worth so I suppose I could do this?

Does anyone have any tips for encouraging the growth of sweet peas?

[mumofstig]

When the plants are small you nip out the top bud to make more shoots grow, too late for that now.

it is important to remove faded flowers though, otherwise the plant doesn't grow any more.

[tosca100]

.....and you only have to nip off the tendrils if you are going for show bench blooms. They need them to grip their supports, otherwise they will end up in a heap.

As mumofstig says, dead heading (or picking very regularly) is important to keep the blooms coming. If they start growing seeds (in pods like peas) their job is done and they will stop flowering, so if you see pods forming nip them off as soon as you can.

[Benandbill]

Thank you both, that clears everything up.  I remember now she said the pods, not the buds - that makes more sense 

[sunshineband]

And don't forget to feed them too -- tomato fertilser does a decent job