After finishing a project, stay in touch with the client and keep looking for related problems you can solve. Think like a partner, not a vendor. Check in regularly and connect your work to their bigger business goals.
You need to approach every engagement with a land and expand mindset. Post-project, stay engaged, maintain the relationship, check in periodically, and stay top of mind. But more importantly, continue to think like a partner, not a vendor. Look for additional challenges in their business that you are well positioned to solve. Connect your work to broader outcomes and show them what's next.
