Do not follow the buyers round, together with your husband, carrying on a continuous monologue between the two of you "and here's a cupboard, it's really handy, did you know we re-did the fascia and guttering on the outside recently, and we've just put in a new boiler, so all those jobs which you want to do when you move house are already done, ha ha ha, etc".
Do not fill every single spare surface with your enormous collection of antique-effect dolls, teddy bears and porcelain elephant ornaments.
Do mention briefly and factually anything which the viewer might actually want to know.
Don't say the bleeding obvious eg "here's the cupboard under the stairs, really useful for storing your hoover".
Don't say anything negative. Obvious but easy to do if you are nervous!
Good luck! We have just sold our house and are now going full steam ahead on finding one to buy.