The answer to this may differ for every person as same is dependent on many variables like personal preferences, location, budget, etc. Here are some of the details that they should pay heed to, at the time of booking.
1. Legality: It's the most important thing to check before buying a flat. In every city there is local government bodies authorized to approve maps of any building. Buyer must check the approvals before entering into agreement or contract.
2. Project Location (Future in Perspective): My views are very different on this particular decision point. It is not necessary always that project on main roads have location advantage compared to the ones located on inside roads. Down the line, after some years you might realize that you have done the mistake by selecting Residential Project located on the main road because of increased traffic sound and commercial activities. Remember we are buying home not office. While selecting any location you should check for basic facilities like grocery store, schools, hospitals, public transport, etc.
3. Price: Well, in the end it all comes down to Price. A buyer must do a complete survey about the prices in location/area in which he is planning to buy the flat/apartment. But there are certain variables which must be kept in mind before you make a decision on the basis of price. These are facilities in the building, specifications of the flat, location, possession date, quality of construction, etc. Also if you like any property and you are not getting it in your budget, don't just walk off but try to negotiate with the builder/developer as I believe that you should not let go your dream home for 5-10%.
4. Features & Specifications: Features are the building facilities and specifications are related to facilities and amenities provided in the flat. Every Builder/Developer gives host of features and specifications to lure buyers. The important part in this regard is to understand which features & specifications are of real use and which are cosmetic.
5. Loan Facility: Generally all reputed builder groups are registered with leading Banks and NBFC's to provide Home Loan facilities to their customers. Whenever any Bank or NBFC approves any project for home loan facility, they provide APF (Approved Project Finance) number to the builder/developer. When customer applies for a home loan, they can just quote the APF number of the project, submit their documents and get loan sanctioned. With APF facility customer is free from the stress of collecting legal documents of the project and submitting them along with his own financial papers. One good thing about project having APF number from leading banks is that this assures you of sound legal & technical credentials of the project.
6. Budget/Add on expenses: Consumer must write down there budget carefully. Property cost is not only the price paid to the builder but there are several add on which you must calculate before finalizing the property. There are add on costs like club membership charges, parking space charges, service tax, stamp duty, registration charges, home loan processing fees, electrification charges, transformer charges, preferred location charges (PLC), etc. Sum of all these expenses is your actual property cost. I have not included maintenance deposit and charges in above list as they do not form part of property acquisition cost but are property maintenance cost. Some Builders have removed all above mentioned charges to make it simple for their customers. Such builders only charge Basic sale price (BSP) for the property.