Recently started the Irish course on the Duolingo site. Have found it to be the most difficult of the three languages I am studying. The most difficulty is encountered when attempting the "Type what you hear" exercises. I do not quite understand the pronunciation, and the spelling is difficult. I would welcome any discussion on this topic.
In addition to the other suggestions, these are things I do: 1) when I encounter an exercise in which the Irish text is shown and the audio is available, I play the audio repeatedly, paying particular attention to sounds that are different than English; I also look away from the screen while playing the audio and visualize the spelling 2) I use three resources to check pronunciation (with the usual caveats about varying pronunciations): a) http://www.teanglann.ie/en/ This site has English-Irish and Irish-English dictionaries, and pronunciation of many words (click the right-most tab after searching for an Irish word to get the audio). The tricky part of this site is that it works best if you have some understanding of they way words vary according to their use in a sentence, e.g. initial mutation (f turns into bhf, etc.) and conjugation b) http://forvo.com/ This is a site with many words and phrases that have been recorded by volunteers. c) http://www.abair.tcd.ie/ You can type a phrase or sentence, and this site will provide computer-generated audio. It isn't as natural sounding as the other two, but it gives reasonable idea of the prosody of the language.
Do you know the IPA? If so, I suggest reading the Irish Orthography article on Wikipedia. Otherwise, try not to force it into the spelling rules of English and learn what sounds go with what combinations in Irish.
You should do an IPA transcription of some of the spoken sentences here, and then compare them to an IPA transcription of the written text one of these days.
Thanks. I laughed when I saw you comment about not being happy with it being posted on Duolingo. I'll be sure not to any more, or at the least give a warning about its accuracy.
It's definitely one of the best videos out there, honestly. But it's not without its faults, sadly. So keep posting by all means, but probably give a warning.
The need to distinguish the sounds that you hear is far more useful than the ability to accurately reproduce them, at this stage of the game, if you are still struggling to understand the spoken exercises on Duolingo. For that purpose, the video that Proinsias linked to will be very helpful, because it will help you to see where your automatic assumptions about what letters are associated with which sounds, and in particular how vowels and consonants interact, have to change for Irish.
Once you familiarize yourself with the basic rules of the mapping between certain groups of letters and the equivalent sounds, then the "type what you hear" exercises in particular, and the Irish spelling in English to Irish translation exercises will get easier (Irish spelling is more regular than English spelling, by and large, though the regional variations do have to be taken into account).
You also have to bear in mind that the current speaker has a regional accent - in fact she doesn't actually speak the version of Irish that the course purports to teach, and she diverges somewhat from the written text in a few cases (most noticeably in plurals). "Tuning in" to her particular accent won't necessarily help you with interpreting speakers from other regions, but will help with the exercises on Duolingo.
Beyond that, it's a question of practice, but you will probably get more "bang for you buck" spending an hour going over the Reshkin video than from any other resource, given the particular problem you describe, of trying to map the sounds that you are hearing to written words.
Here is a link to a page which explains Irish pronunciation: http://www.standingstones.com/gaelpron.html I guess the hardest part of the pronunciations are the combination letters such as MH, BH, DH etc.. Try not to think of these as 2 letters as they are used to represent 1 sound similar to PH in English making an F sound, ex. Phone. I hope it helps.