This tip gives basic queries that should be resolved for a successful SharePoint Project.

Are you looking for a public facing site or an intranet portal? Do you need subset of information available on intranet to be published to outer word? Do you want to develop a portal as one stop solution for whole organization or it will be in parallel with various other system with scattered information e.g. user profiles , etc.
What are the maximum users we want to target in next 5 years?
Do you want to pre-plan for multilingual scenarios?
The user policies and permission must be strictly defined well ahead and direct access (without SharePoint user groups) to content must be eliminated. Owners who define will manage the security must be clear and precise and well trained how to manage security in SharePoint. Administrators and owners, who don’t know how to manage security, are the biggest loop holes in the security chain.
Ownership of servers and management is a pain in butt at later stages, so must be documented and defined during initial stages.
Read only search accounts must be predefined. Using administrators as search accounts is a big security loop hole.
Security patches and Upgrades for Windows Servers SharePoint SQL must be scheduled and monitored. Blocking them forever is inviting hackers to dump the system.
Antivirus scans are often ignored during planning stages. Never do that.
It must be defined clearly what all need to be blob cached and duration of caching must be precise and documented. According front end server configuration might have to be changed. You may never want to blob cache secured contents.
To avoid more expenditure on future upgrades maximize utilization of out of box features of SharePoint.
You may never want to expose underlying framework information through headers . Plan for that during initial stages , if it is a public facing site .
You may want to rely on Google analytic to understand Visitor flow and improvise the site accordingly during later stages . Plan for this .
What might be the external systems from where information flows in or goes out of SharePoint future system . Plan security and minimize / define and document the limitations .
Do you want to go for automatic TFS / 3rd party deployments or want a more controlled deployments with dedicated administrator ?
Have you take sign off on all the relevant SharePoint features to be accommodated in the ecosystem with capacity planning and infrastructure involved to avoid performance hits at later stages?

A few questions to be answered before you start a SharePoint project