New cornets are a significant investment for a brass musician. Those looking for a new instrument thus first should consider the limitations of their budget. They also must try and listen to many different cornets, getting advice from professionals and choosing a new cornet for the tone and quality of the instrument instead of how it looks.
In general, when buying a new cornet, it is a good idea to spend as much as the budget allows. Some excellent deals are available from some dealers and stores, so it is not possible to say that a cheaper new cornet is not a good one, but typically, a higher price translates to better quality materials and manufacturing. The result is better overall playability and tone, as well as a decreased risk of major malfunctions. In the long run, shelling out a little more for a higher-quality instrument will save the player money in both repairs and having to buy a new instrument once the old one is outgrown.
Next, try many different cornets. Every model is a little different, and because no two players have the exact same facial structure, embouchure and hand size, those wishing to purchase a new instrument must choose for themselves what instrument is the best match for them. In fact, some different models within the same line might have slight differences, so once a person has settled on the type of cornet he wants, play as many of that type as possible to find the best one.
When it is time to try each new cornet, try the instrument on a familiar, comfortable mouthpiece which ideally is of at least slightly better quality than the mouthpiece that comes with the instrument. A good mouthpiece can vastly change how the cornet plays, so do not axe a new cornet from the potential "to buy" list until it is clear that the cornet still is lacking even with different mouthpiece options.
Another good tip for buying a new cornet is to check market listings for the instrument. Compare the manufacturer's suggested retail price for new instruments with the market value of the same models that are used. This should provide some concept of the depreciation rate for the instrument. Pick an instrument that keeps its value well over time in addition to having good tone and playability. This lets the player sell the cornet if desired with a much less significant amount of loss.
Salespeople in music stores often sell cornets. Many of these salespeople are not cornet experts. Some even have deals with manufacturers that provide commissions for sales on particular instruments. Thus, it is often better to talk to professional cornet players, cornet and trumpet teachers at the university or college level and independent dealers who have direct relationships with the manufacturers.
Lastly, do not be swayed by only the aesthetics of the instrument. Manufacturers offer many different finish options, many of which look amazing initially. The problem with these finishes, which often are just painted, is that they chip and are damaged easily. Some etchings on the instrument are a better choice for beauty and individualization.