Find what is already doing a job
Before changing anything, list the current pages, forms, downloads, contact details, and external services. Note the pages customers use and the questions your site already answers well. If analytics or search reporting is available, use it to inform that inventory.
An old-looking website can still contain useful work. Good service explanations, detailed project examples, and frequently shared pages may deserve a new presentation rather than deletion.
Map the old website to the new one
Decide which pages stay, which combine, and which no longer serve a purpose. Where an important URL changes, plan an appropriate redirect to the relevant replacement. Sending every old link to the homepage rarely gives the visitor what they expected.
Keep the domain, DNS, hosting, business email, and connected services in view. A website launch should not accidentally become an email migration. Record what each account controls before changing it.
Check the customer journeys
Test the experience a real visitor will have: opening a service page, tapping a phone link, sending a contact form, joining a list, or following an appointment link. Check confirmation messages and where submissions arrive.
Review the new site on a phone as well as a desktop. A beautiful wide layout is only one part of the experience. Navigation, readable copy, and clear calls to action matter at every size.
Treat launch as a handover, not a disappearance
Record what changed and keep the old page inventory. Check that intended pages can be indexed, links resolve, analytics receives events, and the new forms work. Watch for issues after the switch.
No responsible redesign process can guarantee unchanged search rankings. Careful planning does, however, give you a better way to preserve useful material and spot avoidable mistakes.