''To have''

There is no verb 'to have' in Gaelic, so instead people say that things are 'at them'. Use the verb 'to BE' and the preposition 'aig' (= at).

Tha (noun) aig (noun/person).
BE (noun) at (noun/person).
(noun/person) has (noun).

ex. Tha cupa cofaidh aig Ruth. Ruth has a cup of coffee.

'Aig' (like most Gaelic prepositions) conjugates according to person. This means that if you want to say something such as 'She has a banana', you have to use the correctly conjugated 'prepostional pronoun'.

aig + i (she) = aice

Tha banana aice.
Be banana at-her.
She has a banana.

Conjugations for aig:
agam = at-me
agad = at-you (sing.)
aige = at-him
aice = at-her
againn = at-us
agaibh = at-you (plur. & polite)
aca = at-them

Other Examples:
Tha bean aige. bean = wife/woman
Tha duine aice. duine = husband/man/person
Tha leabhar againn. leabhar = book
Tha taigh agaibh. taigh = house

Some Expressions:
Tha fhios agam. = I know.
fios/fhios = knowledge

Tha gaol agam ort. = I love you.
BE love at-me on-you.
gaol = love, ort = on-you

Ciamar a tha thu?

Ciamar a tha thu/sibh? How are you?

Tha gu math. I'm well.
Glè mhath. Very good.

Tha gu dòigheil. I'm all right.
Ceart gu leòr. Right enough/not bad.
Chan eil dona. Not bad.

Tha gu dona. I'm bad.
Tha mi tinn. I'm sick.

Tapadh leat/leibh, ciamar a tha thu/sibh fhèin? Thank you, how are you yourself?

thu (you sing.)
sibh (you plural and polite)

leat (with-you sing.)
leibh (with-you plural and polite)

Check out Unit 1 of BBC's Beag air Bheag for sound recordings of some of the expressions:
http://www.bbc.co.uk/alba/foghlam/beag_air_bheag/units/unit_01/

Greetings/Goodbyes

Halò. Hello.
Madainn mhath. Good morning.
Feasgar math. Good afternoon/evening.

Chì mi a-rithist thu/sibh. See you again.
Chì mi a-màireach thu/sibh. See you tomorrow.
Chì mi thu/sibh Diluain. See you Monday.

Tìoraidh. Cheerio.
Mar sin leat. Goodbye.