Measure from the inside of your doorjambs. Be careful to note how wide your doors can open, and accommodate for doorknobs. If the doors can be removed, that might be a good idea to prevent damages. Always try and choose the doors that might offer the most generous space.
Measure the width of your stairway (taking account if you have a handrail or post), and the height from the top and bottom steps to the ceiling. Be sure to look out for any sloped or curved surfaces. If your stairwell has a landing, make sure your piece can fit on and around it, both width and height.
Account for any low-hanging ceiling lamps or fans, breakable decorations that cannot be removed, stairway banisters or turns, or angled ceilings or walls. Be sure to completely clear a path for your piece; it’s always helpful to make more space than you think you’ll need, if possible.
Be sure that every hallway on route to your final destination has enough room to accommodate your piece, especially if you anticipate any twist or turns you may have to make. Measure the height, width and depth, making sure the shortest measurement of your furniture is less than the width of your hallway.
Plan your route and clear it out. Make sure you have a good game plan on how to get your furniture to it's final location. Planning ahead can save a lot of time and hassle when your furniture arrives. Remember, the quickest route might not always be the easiest. Plan for all the twists and turns that it might need to take as it enters your home.
Don't forget to measure the area around the entry point you plan to take your furniture in. Be aware of gates, porches, outdoor, and flower beds just to name a few. This always includes building lobbies and all paths to your apartment, loft or studio.