The traditional method of growing in a greenhouse was to plant straight into the soil, which is fine... it gives you maximum height for growing. However your soil will be slightly cooler than if you grow in bags or tubs, you’ll need to dig over the soil thoroughly and also rotate your crops. If you opt for growing in a ground bed try to build a mini raised bed confining the soil with timber or blocks. Most people find it easier to use bags, pots or tubs to grow in. It means you can move the plants around and it keeps the soil slightly warmer. You can also easily dump the used soil onto the compost heap to rejuvenate the soil at the end of each season. Or you could use a combination of both... ie a ground bed down one side and bags/pots on the other.

Most people put a walking path or pavers right down the centre of the greenhouse which if you have a narrow greenhouse is logical, however if you have a wider greenhouse such as 8ft or wider you could think about having 3 rows of plants left, right and centre and have two smaller paths down each side. With this layout the plants will benefit from the height and space that is available.

Also see here for examples of other greenhouse layouts.