I've always programmed alone, I'm still a student so I never programmed with anyone else, I haven't even used a version control system before.
I'm working on a project now that requires knowledge of how programmers work together on a piece of software in a company.
How is the software compiled? Is it from the version control system? Is it by individual programmers? Is it periodic? Is it when someone decides to build or something? Are there any tests that are done to make sure it "works"?
Anything will do.
Actually, there are as many variations on these processes as many companies there are. Meaning: every company has a little bit different conventions than others, but there are some common best practices that are generally used in most places.
These simple things ensure that the project doesn't go out of control and everyone works on the same version of the code. The continuos integration process helps when something goes terribly bad.
It also prevents people from committing stuff that don't build to the main repository.
If you want to include a new feature that would take days to implement and it would block other people from building (and testing) the project, use the branches feature of your version control.
If that is not enough, you can set it up to do automated testing, too, if that is possible with the project in question.
The above list can be very heavyweight at first glance. I recommend that you follow it on an as-needed basis: start with a version control and a bug tracker, then later on set up the continuous integration server, if you need it. (If it's a large project, you're gonna need it very soon.) Start writing unit tests for the most important parts. If it's not enough, then write more of them.
Some useful links:
Continuous integration, Daily builds are your friends, Version control, Unit testing
For version control, I tend to use Git for my personal projects nowadays. Subversion is also popular, and for example, VisualSVN is quite easy to set up if you use a Windows server. For client, TortoiseSVN works best for many people. Here is a comparison between Git and SVN.
For bug tracking software, Jira and Bugzilla are very popular. We also used Mantis at a previous workplace.
For continuous integration software, there is Teamcity for one (also, CruiseControl and its .NET counterpart are notable).
Of course, that would be the lead developer.
In companies, the lead developer is the person who talks to the financial / marketing people of the project, and decides the arcithecture according to the financial capability of the company, the planned features the requirements from users, and the time that is available.
It is a complex task, and usually more than one people are involved. Sometimes members of the team are also asked to participate or brainstorm about the design of the entire project or specific parts.