Line management is currently on my mind as I've recently joined Masabi as VP of Engineering for our 20+ strong development team. Coincidently it's also something I've recently been asked about by a peer in a similar position. Modern management practices tend to frown on line management as it smacks of traditional organisational structures. However - out with line management tends to go any formal pastoral care for staff as well as inexperienced or unqualified people getting left to deal with complicated situations with little or no guidance.
Below is advice based on my experiences. I'm happy to answer any questions, but I don't present anything here as a shining example of good or bad ("where's the Holacrocy dude?"), just stuff that has worked well for me over the years.
Everyone needs good guidance
I wrote this article on Roles & Responsibilities in Software Teams over 5 years ago and have used these effectively in 3 companies now. I find it really helps for everyone to be clear on what's expected of them, it certainly makes the line managers job easier to have something which defines positive (and negative) behaviour.
Team Lead as line manager for the team
In my roles above, the Team Lead is basically line manager for the team. Their most important line management duties is regular 1-2-1s with their team to make sure everyone's happy and productive and catch any situations or issues arising quickly. The Team Lead will also deal with team related line management issues, such as approving holiday, work from home requests etc.
The CTO/VP/Director/Head of Dev (i.e. me) will have more frequent 1-2-1s with the Team Leads than other team members so there's a good feedback loop and any issues can quickly get escalated if needed.
Team Lead != Lead Developer
I intentionally separated these roles of Team Lead and Lead Developer, as being good technically does not make you a good people/line manager (see the Peter Principle). In many teams I've looked after the same person holds both roles, but not always.
Ultimately I'm the Line Manager though...
When it comes to more substantial issues such as anything requiring expenditure (e.g. pay increase requests, training) or performance issues that the Team Lead cannot solve himself (e.g. when you're getting near the realm of disciplinary proceedings) that's where I will take over from/support the Team Lead. Ideally a team can work through most of it's issues, but not always.
Line managers need good guidance and training
Looking after people comes more intuitively to some than others, but either way it is a discipline people need training and guidance on - how to give good feedback is a great example as are good listening skills. I make an effort to mentor Team Leads in my 1-2-1s with them, but it's good to have wider organisational initiatives too.
Pay reviews and performance appraisals
I've written up about my experiences with pay, performance and feedback previously. I consider regular 1-2-1s (with Team Lead and myself) to take the place of annual performance appraisals. However most companies still do pay reviews annually, which means some form of annual pay review meeting is required. As something I'd consider a more substantial line management issues I personally take responsibility for those pay review meetings with all my staff.