If you're about to renovate, it's smart to inspect your home inside and out. Make note of obvious damage and defects you'd like to fix along with parts of the building you'd like to modify. It's important to allow sufficient time for this, and even when getting quotations build in a reserve for delays during the renovations.
Bring in experts
Depending on the extent of the work, experts such as an energy consultant, architect, carpenter, cabinetmaker, painter, etc. must be brought in. Experts see more than a layman and can also determine whether the insulation of exterior walls and the roof is sufficient, whether new windows must be installed and how the facade can be designed accordingly.
It's worthwhile to have a building assessment when renovating windows, attic floors, cellar ceilings as well as roofs and exterior walls.
After these preliminary discussions, think about which modifications you would like and, if necessary, divide up the work into two categories - that which is urgently needed and that which could also be carried out later. In this way you make the financing easier and protect yourself from the feeling that you've taken on too much all at once.
Perform a cost/benefit analysis
Discuss your specific renovation requirements with the experts and check whether everything is feasible. Get some bids and also ask about the time needed for construction.
Think over carefully whether the planned improvements are worth the expense. The future market value of an older building which has already been renovated can, for instance, be higher than combination of the purchase price and the renovation expenses; on the other hand, if a possible sale is planned, don't expect to get your money back on every single extra.
Watch out - it's not unusual that someone does an inadequate job of checking financial options and hands out project contracts without getting competitive bids or without an overall budget cap.