Markets change all the time, so a strong focus on a particular area can give you a good idea of when might be the right time to enter an emerging neighborhood or developing area. Unless you have time and money to burn, you want to manage to be just on the cusp of other development to drive traffic and desirability to your project.
Consult local experts, talk to other owners and get a feel for the area as part of your project identification process. A localized consultant can be valuable here. This is someone you pay to be your eyes and ears in a particular area and bring potential properties to you.
The right time may not be completely obvious and may rest on a number of conflicting variables and metrics. The more research you do, the better your ultimate development plan will be (which helps a lot with the financing phase, too).

When you identify a prospect – either an existing building or vacant parcel – you begin due diligence and evaluation of the project. Depending on the market, you may need to move quickly, so some parts of this phase can happen concurrently.
You will develop at least a notional plan of what kind of building you want to build. This includes a draft schedule, developmental budget, and ideally a strong team of principals involved. At this stage you need to at least secure the involvement of a top quality project manager, even though there isn't actually a real live project yet.
Identifying obstacles and projecting both best-case and worst-case scenarios happens here. The hardest part there is thinking realistically. If you don't feel you can rely on your own experience, there are development consultants who specialize in that sort of thing.

During this phase, the project's planning and budgeting moves into high gear. Architectural plans, environmental studies and permit applications are in their preliminary phases, but they greatly resemble the final documents that will be deployed during the construction phase.
Project contracts and financing plans are also drafted but not finalized until the end of the process. But it's very important to have sources of funding identified and in place during this phase.
Your project development team should also be identified and put in place during this phase. That includes architects, engineers, your on-site foreman or a dedicated project manager and some of the more specific skilled tradespeople you may require.
You will also likely need a legal team to begin filing paperwork and obtaining permits or other necessary government approval.

As you move into the development phase you start planning out real schedules, securing and finalizing financing, and executing all project documents.
The development phase begins with a complete design review from all aspects of the team. If necessary, you will issue change orders to the plans based on their input. Contracts and financing can then be executed with the knowledge that a completely vetted plan is in place.
When construction begins, every project will still have its share of open questions. A good design and a good team must be flexible enough to accommodate a changing reality. Most importantly, a realistic schedule and budget will have room for overages in certain areas while also pre-planning areas that can be reduced in scope if necessary will also save time and money.