How to Buy a Harp
The first thing to know is what you plan to do with your harp. Someone who intends to play in an orchestra needs a different kind of harp than someone who wants to play for harp therapy on in a Celtic band or who just wants to play for their own pleasure. Only the first of these dreams necessitates a pedal harp whereas the latter three are better fulfilled by a lever harp.
Next, it will help you to have some idea of what you plan to play on your harp. If, for instance, you want to play Celtic music, then that suggests a lever harp that is not too heavy, somewhat smaller and has top quality sharping levers. Also, many of the Celtic professionals prefer to have a harp with a range down to the A two octaves below middle C, so you might take that into consideration. If you are wanting the ability to play a range of classical, pop and modern music, than virtually any well-made moderate string tension lever harp will work for you.
If a lever harp is your intended prize and your are beginning the search it is wise to be aware that within modern lever harps there is a sub-group increasingly thought of as pre-pedal harps. Pedal harp lutheries and a handful of lever harp lutheries, make harps that have levers but also have high string tension and the type of heavy strings designed to prepare a player to ultimately evolve to a pedal harp. This is the route to go if pedal harp is your goal. If you are not planning to be a professional pedal harpist, stay away from pre-pedal lever harps because the overall weight of the harp and the heavy string tension will limit your choices in the future. In general, if you plan to play the lever harp, purchase a harp made by a lever harp lutherie.
Another important thing to know is that many pedal harp teachers have very little knowledge about lever harps. This is a function of an age-old problem in the harp world and is absolutely not the fault of any specific person or harp teacher. They believe, because they played a pre-pedal harp while they were learning, they understand lever harps. Additionally, most of them were very focused on pedal harp and the necessary technique as their goal. This is probably what made them successful pedal players and is not to be diminished, it simply means that they have only very, very limited knowledge about this other instrument, the lever harp. Your harp teacher may love L&H pedal harps and think highly of their lever harps, but most lever hap professionals beg to differ - in large numbers - so shop, shop, shop around!
One little thing that can turn out to be a huge thing is the harp warranty. Different lutheries warrant their harps for different amounts of time. Check it out before you buy, it will tell you two things: how long you are protected and how much faith a given lutherie has in their instruments.
If you forget everything else, remember this, buy a harp you absolutely love. The more you love your harp, the more you will play and the more joy you will take from playing. There IS something special about playing the harp and you should be playing a harp that reflects that back to you.