Decide how you're going to dispose of the spoil. Traditional method is to make a rockery <yawn> near to the pond, which should preferably enjoy full sunlight for most of the day.
We made a rockery, of course, incorporating lots of "caves" of various lengths and diameters of plastic pipe for frogs and toads to hibernate in, accessible from the pond margins. Some of the spoil, when we got down far enough, was a red clay suitable for rustic pottery.
Make the whole thing more interesting by designing a watercourse from near the top of the rockery. Don't skimp on the pump - get one that's reliable and capable of pumping a high volume of water to a reasonable height - you can always reduce the flow if necessary by using a small diameter hose, dialling back the volume if it's a really posh pump, or fitting a fountain attachment. Bury the hose in a larger diameter waste pipe so you can replace it at a later date if necessary without having to dig up the established rockery. Take great care over burying the power supply where you can locate it again and using high quality electric fittings.
When you've decided on the dimensions of the pond, make it at least twice the size you first decided. Trust me, you won't regret it.
Make the pond at least 90cm deep, with shallower margins for plants. Research the marginal plants to avoid the more problematic species, like water mint - it's great for bees, but very invasive. Use the best quality liner you can afford, and protect the exposed edges from sunlight as much as possible, with overhanging stones - we bought broken Yorkstone flags, which have been brilliant, but a hell of a jigsaw puzzle. Enough for now, maybe some pics over the weekend so you don't repeat our mistakes!