What should I consider before buying a new climbing harness?

Which climbing harness you should choose depends on what kind of climbing you practice and what particular requirements are most important to you. These can, e.g. be the following:

1.Comfort / padding
2. Specific size
3. Number and purpose of the equipment loops
4. Self-closing buckles
5. Climbing harness type and who will be using the harness

Size
You may find that different manufacturers have different measures for what is labeled small, medium and large. The small can fit perfectly in one brand, but in another you are somewhere between small and medium.

Equipment Loops
If you are climbing long sports routes, traditional or ice climbing, it is a good idea to have at least the 4 standard loops that most harnesses have. But if you only want to climb indoor climbing walls and competitions, it becomes more important to get at as lightweigth a harness as possible. Ie with as few loops as possible or completely without.
Be aware that equipment loops can have different breaking load, which you can find in the individual manufacturer's description of the harness.

Self-locking buckles
Today, the vast majority of climbing harnesses come with self-locking buckles, but you may find that some harnesses have a buckle where you have to guide the strap back through the buckle for it to lock properly. Since it's a human factor that can be forgotten, Gubbies recommends the self-locking buckles.

Legs loopsClimbing harnesses come with either fixed or adjustable leg loops. Whether you want one or the other is a matter of taste, as the need to be able to adjust its leg loops only rarely arises. The buckles add extra weight and make the harness more expensive against having an ability that most experienced climbers rarely use.

Haul-loop
On many choices you will find a 'Haul-loop' centered on the back of the hip harness. It is a loop that can be used for a variety of purposes. For example, the climber's buddies may special situations hold on to it, climbers may have a chalk bag or extra rope attached therein, or may be used to - on long outdoor routes - have luggage hanging in.