Get some instructional materials such as CDs or DVDs that will teach you the basics of Gaelic singing. See Resources below for online sites or contact Gaelic singing groups and folk bands for further advice and materials.
Decide what type of Gaelic song you want to sing. Both Scotland and Ireland can lay claim to Gaelic music and have different types of songs ranging from psalms and spiritual ballads to traditional work songs and dancing tunes. Decide which best suits the occasion and your level of experience.
Choose a song that suits your voice. Some songs will be better suited than others to your voice type. Select one that has a melody that you can easily identify with and that compliments your voice.
Pronounce Gaelic correctly by learning parts of the language and listening closely to others performing and speaking Gaelic. Some sounds can be quite harsh and nasal but are softened when singing. Learning from others by practice and imitation is the easiest way to achieve correct pronunciation.
Understand what the song is saying to truly appreciate the meaning and be able to identify with what you are singing. Especially if you are performing to a knowledgeable crowd, your singing should reflect the mood and convey the meaning of the song you have chosen.
Go to a Gaelic music festival to practice with others and perform in public. Most Gaelic music festivals take place in the north of the country but if money is no object, take a trip to Ireland or Scotland and participate in the "National Mod" or "feisean" for a truly authentic experience.