Do your research
You must not buy without trying it out.

What’s it made of?
A combination of feather and foam is comfortable and will spring back when you stand up better than full feather cushions.

Review access
Can it fit through the front door or around stairs?  If not, can the window be removed? This is relatively simple if carried out by professional movers (get a quote first).

Shape
Consider the shape carefully. It’s a big ticket item and will last for many years, be careful of following trends.

Budget
Buy the best, most well made sofa you can possibly afford.

Fabric choice
Source your own fabric if you don’t like what the manufacturer offers. This is a good way of upholstering a simple good sofa in a really good fabric or just getting the fabric you want. The sofa company will want to check the fabric for suitability.

Fabric quantity
Always check the quantity of fabric required, it’s a surprisingly large amount, approximately 18m for a 3 seater sofa.

Fabric practicality
Be practical when choosing the fabric. You have to be a non children/non red wine household to get away with white sofas. Patterned, textured fabric is far more forgiving than plain fabric. Leather is incredibly durable but I find it cold in the winter and hot in the summer. Think about the seasons, are you going to want to sit on a velvet sofa on a boiling hot day?

Remember it’s got to look great AND be comfortable.