I put a lot of potential leads in my crm.

Some af them becomes client and contactperson (onther the cliënt)

How can i manage that the leads that come in (through putting it self in the system, trough social media connection, trough connection with my contacts from google) are checked with my clients and contactpersons, so that there are not put double in the system?

I would like to automise this, because otherwise it's cost a lot of time.

any suggestions? or a solution for this?