If you've got a lot of work contacts, you probably want to keep them organized, grouped together, and separate from your friends and family. If you can't be bothered creating multiple folders and subsections for your contacts list, try reader trickycoolj's simple trick instead.
I add the company's initials to all my work contacts in my personal smartphone (i.e. "COMPANY Last, First" or "COMPANY First Last"). Keeps the admins, team members, supervisors, and managers all clumped in one spot in the contact list.
This can also help to minimise misdials when you're trying to contact friends with the same name - which is especially handy if you're prone to drunk dialling your mates in the middle of the night. We're pretty sure the client for that big project you're working on doesn't want to receive a "hilarious" text at 3am.