Ask HN: managing clients, contacts and leads

What software, or other methods, do you use to manage your client contacts and your sales leads. I find it difficult with to work effectively when we don't really have a holistic system for recording customer communications.

Obviously one needs to record the basic details, email address, phone number, etc.. But then also details of each call made with them, perhaps copies of all emails from/to the client, etc..

How you're actually managing all this now and how well it's working. How would you do things differently if you were starting fresh. Thanks.