Do engage an architect for any structural changes. It is important to find one who will take the time to understand your property. This will ensure a sympathetic renovation. Many city councils that have heritage listed houses will have architects on their books, who specialise in renovating period houses. Some will even provide a free concept sketch.
Do let the building talk to you. For example, if the old light fittings are gone then you can choose a completely new style rather than commissioning a copy. Often old houses will have already undergone several renovations in their lifetime. Peeling back the layers may reveal a decorating treasure.
Do use recycled products when restoring an old house. They are more likely to fit in with the rest of your house. This is also the green option. Otherwise go for completely new so that the contrast between old and new is exaggerated.
Don't be tempted to seal the house up. If possible, steer clear of double glazing. An old house needs to breathe. Don't use cement over old stone. The old stone may crumble away leaving you with an unsound structure.
You don't need to include every period fitting that you can discover. Not everything from your houses period was in your house originally. Better to stick closely to what your house is telling you. But if you really love it, get it. It will always be a talking point. It just may not increase your resale value. Be sensible about the things you love. An open air Balinese bathroom works well in Bali, not so well in Connecticut, and probably not very well in a period house, unless that house is in the tropics.
Remember a renovation is always going to cost more that your original quote. It is best to budget for at least 50% more and then aim to stay under the original price. Old houses have a way of throwing up surprises.