Rehashing a previous comment on how I look for good marketers:
1) Look for someone that has experience working big and small companies. Big brands will train comms, project management, procedure and how to think at scale. Small brands give 'getting it done' skills, generalist experience and show they can get technical/dirty hands. Larger brand experience typically looks more impressive but often work has been project management for agencies and doesnt suit hands on efforts or creativity. Likewise if you're business is big enough to run agencies if someone has always been hands on they often struggle as project managers and understanding how to communicate needs in a way that translates effectively downstream.
2) Dig into exact contributions for past roles. Ask for logic that lead to decisions. Often marketers talk about great campaigns results but really they were a body in a room with little input. Dig for detail and motivations to decisions and you will find out who is who.
3) Look for initiative with intelligence. Many solid looking marketeers repeat what is always done, optimising here and there. That suits some roles and businesses. There's an unrecognised value in the solid citizen employee. But for smaller business looking for exceptional results you need someone who will see the world independently of the compaineis previous activites, and most likely their previous roles. In this repeating and optimising wont work. Ensure you find people that introduce campaigns and activities with originallity if you need new oppurtunity and delivery.
4) Experience counts. It's easy to be attracted to enthusuasm but confidence/enthusiasm and ability are often confused. Look for someone that has done things. When looking at people with higher level expereince ensure they can get thier hands dirty. Make sure they have the ability to learn and adapt vs puely strategise.
5) Don't go cheap. I often see startups advertising low paid marketing roles, while they pay for experienced developers. Half the price sounds great but they will bring a fraction of the value.
6) Find someone that can analyse data vs report it. There's a big difference in the 2 and the former is surprisingly rare.
7) Avoid anyone that shows narcissistic tendency or is generally 'me' focused. This personality tends to be bad comms people (especially with social) as they see the world from their POV, not the customers. Also your risking a tough working enviroment. Look for things like how they delivered on a job they felt was wrong or lacked value as well as the usual egocentric viewpoints when they discuss marketing examples.
8) Look for someone that lives marketing beyond thier job. A person that can talk about companies beyond their own and the role they've likey researched for. Look for interest in the wider industry/technologies vs focusing only on thier job.
9) Dont stress about direct inductry experience. Unless there is incredibly niche market knowedge or contacts needed a good marketer will be good regardless of product. Thats said you need the right marketing category. A EDM specialist can likely shift to PPC, but events, PR are entirly different. So people lump marketing together but the fields are entirely different.
10) Sales and marketing are not the same thing. Know what you need. They dont often come all-in-one.
11) While not an absolute I usually check linkedin contacts to skill endorsements ratio. Typically this ratio is higher for the people I know are good marketers. I wouldn't make my decision by this but is seems one of those soft indicators.
12) When you interview give a 10min exercise before to discuss and cover up real-time actual skills. E.g. show them some relevant to role campaign materials (e.g. landing pages/EDM's) and ask them how they would improve. Ask them what they would do with $50k. Typically I add in some spelling/grammar mistakes to also look for attention to detail as it tends to be a 'you have it or you dont' skill (like initiative) and not something you can train up.
Once onboard;
13) Make sure they have a budget. Dont think the salary is the budget and then they can write viral blog/FB posts. Generally I'd say a 10-20x marketing salary would be a good rule of spend if bringing a permanent marketing role in.
14) Give marketers product input. They should have their finger on the customer pulse and valuable views on what sell/motivates users. Dont let tech side shut out marketing.
With the coding thing, I have to disagree there. In 15 years of marketing I've never seen that correlation. 100% agree being tech savvy is useful, especially in setting up testing and tracking tools but an actual coder... not from my experience.