I know IKEA well from living in London.
I advise you to go late at night and/or midweek if possible. Less crowded, more chance of grabbing a staff member for help.
Can actually be pleasant, but not at weekends when it can be hellish. Don't go there with a hangover or in a bad mood. IKEA is not known for helping with those.
Food there is handy, quick and good for refuelling the tank, not gourmet but good value (at least it was in London, not sure about Belfast).
You can take shortcuts, but sometimes its easier to go with the flow.
Obviously do your research first, online or catalog. Bring measurements.
IKEA have some good stuff and some absolute rubbish. You need to see it to figure out which is which. Some good bargains for basic things.
Didn't think much of their sofas but maybe they have changed.
Personally I would not kit out my whole house from IKEA, that might be considered a bit naff ;-) But up to you.
Generally the IKEA stuff is reasonable to assemble once you get into it. Definitely recommend a power screwdriver or drill that can do same.
There are a whole lot of fixings for most items, but that is definitely a plus as it makes them strong.