The relationships you need to develop can be described as either a triangle or square. Let's start with the square. Musical Artist X is trying to build a square with four corners:
1. Record Label
2. Booking Agent
4. Public Relations Expert
Now, let's look at this from the perspective of a new band. Of the four, perhaps only one is going to be initially obtainable: Record Label. There are tons of them. The ones that are going to put out the record of an unknown band are going to want finished songs, so the first piece of advice is "figure out how you are going to record some songs that a record label will WANT to put out."
Assuming you have accomplished recording your music, you want to put out a series of records in the course of a year, culminating with a full length release.
Ok, so you've done that. So now you are looking at Booking Agent, Management, Public Relations Expert. Hopefully you are releasing a record on a label that has a Public Relations Expert available, if not- good luck. That leave two corners of the square: Booking Agent, Management.
Now, if you are super lucky (or totally unlucky) you will get Management first. If you are like most bands, you will not have any management, leaving the next achievable goal after "Record Label" to be "Booking Agent." This is where it gets somewhat confusing and unfair in that the best way to get a record label that can afford to release and promote your record is to have a booking agent and vice versa. Outside of that happy/paradox solution, a band needs to embark on DIY touring: FOR THE PURPOSE OF INTERESTING A BOOKING AGENT.
DIY touring can be a necessary step, but it is not a solution in and of itself, in fact, if you try it more then once or twice you may end up not having a band. Thus, when considering the problem of DIY touring you want to think about two choices: Developing a draw on a regional circuit or attending special events. Attending special events is a route oft-taking and is often a recipe for failure. If a band with zero corners of it's square set up tries to take SXSW by storm- it's going to be a failure. On the other hand, regional touring is a strategy that can work in conjunction with day jobs so longs as the group members are savvy.
If you can steadily approve your draw on a regional basis in conjunction with releasing records, you should eventually land some kind of booking agent. Alternatively, you might be able to obtain a manager, but if you get a manager before you have a booking agent, that manager better get you a booking agent first thing.
Once you have joined a Record Label with a Booking Agent you are ready to tackle the remaining corners of the square: Hopefully, obtaining a Booking Agent will get you on a Record Label that has Public Relations OR Management that can either the Public Relations for you. After all four corners of the square have been established, the young Artist will now be a professional Musician.
A variation on the square is to knock out one of the corners in the square to create a triangle: this requires one of the remaining three corners to do double duty. The typical combination is Record Label/Public Relations, but one of the impacts of the collapse of the music industry is that having a Public Relations expert independent of a Record Label is more feasible then it once was.
Thus, for a new artist the goal may be to set up a triangle, with the idea of broadening it to a square or creating a different combination for their existing triangle (for example. instead of combing record label/public relations, combining management/public relations or management/record label.) The new iterations are a manifestation of the decline in power of Record Labels.