Hi LyndaW. There has been much good information, obviously conflicting as we are not all the same and don't have the same likes/wants/needs etc.
I wanted to add that I am a rotten sailor and it took thirty odd years before I took my first cruise. Thereafter I was hooked.
The main point is that you need to choose a cruise-line and ship that suits you. For instance, we regard ourselves as 'young' so ruled out some lines. We ended up (although we have cruised with four different lines but always return to our favourite) with Celebrity, an American company. They have a 'can do' feel about them.
If you prefer afternoon tea served by staff with white gloves with Rule Britannia playing gently (can it be played gently?!), Celebrity is not for you. If you prefer six-star hushed service, it is not for you. If you prefer much noise and high-jinx by the swimming pools, Celebrity is not for you. That is not to say that any of the above are not fine, just not for us.
Celebrity is a 'premium' company at a level just before one reaches the six-star level. The cabins on their ships are the best we have encountered with some on the later ships absolutely brilliant (this is in terms of space and clever layout etc.).
Food on Celebrity has deteriorated slightly - as have they all - in recent years and we noticed that they are combining two courses at supper but we can live with that!
Safety is paramount (on several levels) and from what we can see, they are vigilant which is reassuring.
We love the evening entertainment, just like seeing a west-end show but hate the rush from (usually) one end of the ship to the other (where the theatre is situated) as our table is often the last to leave the dining room! Gassing too much.
In terms of table size, again personal preference is key but we always ask for a large table - eight or ten. This gives adequate opportunity to move around the table and converse with others - being stuck with one set of people could be tricky! We also always ask to sit with some non-Brits, too. We love the different dimension this gives and are still 'email friends with some of them, years later.
It may be helpful for you to attend a Cruise Show - there are a couple around the country and then you could pick up brochures - but do try to read between the lines! They all want your money!
Although we enjoy mid to large ships, there is always somewhere quiet to sit and read - either on the day-beds at the very top of the ship or sitting at the back, feet up on a rail, watching the wake as she trundles along in the sunshine. Big is not always bad. Although, we have not yet tried 'enormous'.
Finally, if you have doubts about sea-sickness - I am your girl! In ten plus cruises I had one occasion to go and ask for an injection (no, not to put me down, although I was considering that option at the time...) which put me to sleep for about 12-15 hours. When I awoke, the bad storm had passed and I was fine. Generally, by taking a piece of ginger and a meclizine pill (easily obtainable) I am fine and I am a very poor sailor (once was nearly sick on a pedalo!).
My family cannot understand our love for cruising and our trying to explain the joy of popping up at yet another destination (after sailing overnight) is a mystery to them! We can have a taster-day somewhere without being stuck for a fortnight in a resort/town we hate - and can always return for a longer holiday if we know we like the place.
I hope you choose the right line/ship for you and have a wonderful time (NO packing and unpacking as on a touring holiday. It's just wonderful!).