Projects are complicated. Lots of agreements and changes are constantly made, these should be managed properly.
Document all changes, variations and agreements on your projects. You should put everything in writing.
Short RFP/RFQ/RFT response times reduce the quality of project proposals and ultimately increase project costs. Reduce the chances of this happening by allowing sufficient time for companies to prepare quality proposals.
Projects often fail because the project team members are not clear on their roles and responsibilities. Make sure your project team members know what they are supposed to do with defined roles, clear role descriptions and briefs of what they should be doing.
Manage with contracts to improve your project success. Define scope and roles clearly. Putting a lot of the project work out to contract is one way, with the benefit of being able to control the schedule and cost by applying contract terms. Or contract internally.