What is the importance of the pre-construction stage in constructing a project?

Very important, where the Contract should be studied carefully, to determine project statement of work, organizational process assets and other components to have The Project Charter Document, helps of determine, Preliminary Project Management Plan, Scope, WBS, Preliminary basic time schedule, Cost, Budget, Quality plan, Human resource plan, Communication plan, Procurement plan and finally Risk

Highly important.
In this stage, the operating contractor has to develop the conceptual cost estimate before completing the conceptual design.
The basis for this planning estimate is, the descriptive purpose of the project, general design criteria, significant features and components, the methodology, and any other known research and development as required.
All assumption made within this estimate must be documented fore review and concurrence.
The main purpose of developing conceptual cost estimate at the pre-construction stage is for preliminary budget estimates and to identify scope of work.
We also include the preliminary master schedule in this stage and as it progress we just have to modify it.
These are only some of the most important scopes in pre-construction stage.
I will leave the rest of the scopes for others to share.
I hope this helps.

very important stae. It includes meeting with clients, Contractors and interdepartmental to discuss various aspects of the project in detail. The contractor is briefed on working approved drawings, The client is apprised for arrangement of funds. The Accounts section prepares the documents. 

Pre-Construction stage is the the most important phase in order a project to be successfully executed.
during this phase that critical planning; including scheduling, budgeting, value engineering and quality decisions are made that will have a significant impact upon construction and the final cost of the project

Design and Construction as an Integrated System In the planning of facilities, it is important to recognize the close relationship between design and construction.
These processes can best be viewed as an integrated system.
Broadly speaking, design is a process of creating the description of a new facility, usually represented by detailed plans and specifications; construction planning is a process of identifying activities and resources required to make the design a physical reality.
Hence, construction is the implementation of a design envisioned by architects and engineers.
In both design and construction, numerous operational tasks must be performed with a variety of precedence and other relationships among the different tasks.
Several characteristics are unique to the planning of constructed facilities and should be kept in mind even at the very early stage of the project life cycle.
These include the following: Nearly every facility is custom designed and constructed, and often requires a long time to complete.
Both the design and construction of a facility must satisfy the conditions peculiar to a specific site.
Because each project is site specific, its execution is influenced by natural, social and other locational conditions such as weather, labor supply, local building codes, etc.
Since the service life of a facility is long, the anticipation of future requirements is inherently difficult.
Because of technological complexity and market demands, changes of design plans during construction are not uncommon.
In an integrated system, the planning for both design and construction can proceed almost simultaneously, examining various alternatives which are desirable from both viewpoints and thus eliminating the necessity of extensive revisions under the guise of value engineering.
Furthermore, the review of designs with regard to their constructibility can be carried out as the project progresses from planning to design.
For example, if the sequence of assembly of a structure and the critical loadings on the partially assembled structure during construction are carefully considered as a part of the overall structural design, the impacts of the design on construction falsework and on assembly details can be anticipated.
However, if the design professionals are expected to assume such responsibilities, they must be rewarded for sharing the risks as well as for undertaking these additional tasks.
Similarly, when construction contractors are expected to take over the responsibilities of engineers, such as devising a very elaborate scheme to erect an unconventional structure, they too must be rewarded accordingly.
As long as the owner does not assume the responsibility for resolving this risk-reward dilemma, the concept of a truly integrated system for design and construction cannot be realized.
It is interesting to note that European owners are generally more open to new technologies and to share risks with designers and contractors.
In particular, they are more willing to accept responsibilities for the unforeseen subsurface conditions in geotechnical engineering.
Consequently, the designers and contractors are also more willing to introduce new techniques in order to reduce the time and cost of construction.
In European practice, owners typically present contractors with a conceptual design, and contractors prepare detailed designs, which are checked by the owner's engineers.
Those detailed designs may be alternate designs, and specialty contractors may also prepare detailed alternate designs.

Pre-construction,is so important like we are going to attending preliminary exam before the final! The pre-construction stage in construction field is critical to the ultimate performance of the work.
The services detailed in this section are intended to be performed in conjunction with the design team.
It has been our experience that the final product can be substantially enhanced, from both a product and cost standpoint, if a builder's perspective is incorporated early in the design process.
Opportunities to provide such services are largely governed by the method of contracting chosen for a given project.
Some key steps of these stage:1.Design/pre-construction/construction master schedule development and management Initial pro forma and programmatic budget analysis Construction feasibility reviews2.Project budgets and analysis at schematic/design/construction document intervals3.Detailed post bid analysis4.Personnel, materials, supplies and resource availability confirmations.
Survey entire project site for: a) Existing Deficiencies b) Code Violations c) ADA Compliance d) Electrical/Mechanical Capacity e) Access Issues5.Assist in the identification of Base Building Material Specifications which may require modification/supplementation: a) Curtain Wall/Storefront Manufacturer b) Brick/Mortar Specifications c) Ceramic/Stone Specifications d) Toilet Partition/Accessory Manufacturer Specification e) Light Fixtures f) HVAC Diffusers & Registers6.Arranging to attend a preliminary permit meeting with the local governing agency.
Help identify potential issues that could affect the project schedule.
Establish lines of communication with affected inspection agencies.
There are so many vital reasons are concerns with it's importance which all can't be at all here.