[JayG]

Because seed spuds are rarely spherical, and chits are young roots and shoots I lay them on their sides on a layer of compost and gently cover up - some chits will be up, some sideways, and some down, but they soon sort themselves out! 

If I were using a dibber rather than a trench I'd drop them in chits up, as DD says, and for the same reason.

   

Sorry I disagree with you there JayG. A chit is just the shoot not roots. Once the tuber is planted in moisture the roots develop downwards from the chits as they grow upwards.

Each eye of a potato contains all the cells needed to become new shoots, roots, and stolons (the modified stems which eventually swell to become the new tubers,) and these start to differentiate as the eyes are chitted.

When planted the shoots grow upwards, the roots downwards, and the stolons sideways (more or less!)

This Wiki entry describes what happens (a bit lengthy – it’s in the section headed “potatoes”.)