There are quite a few arrival lounges at the airport where you can shower and relax for a few hours. IMO most hotels will not let you check in early, unless you pay them for the night before your arrival. A cheaper alternative will be to use the arrival lounges and if you travel in first or business on Cathay Pacific or a member of Oneworld's elite tier then it will be free.

http://www.cathaypacific.com/cpa/en_IN/atairport/hklounge_arrival

If not then there are pay lounges, which will be cheaper than hotels:

http://www.hongkongairport.com/eng/passenger/arrival/t1/airport-services-facilities/shower-pay-in-lounge.html

I would use the lounge and hang until around 10:00 AM then try and sweet talk my way for an early check in at the hotel.

Hanuman, You never fail to come forth with good suggestions. I've followed so many of your posts. Thank you for the suggestions regarding my question. Unfortunately we are not in either first or business class, though we will be flying in on Cathay Pacific. Thank you for the links. I'll check into them.

book at a chain hotel and the chances are 50/50 that you will be given a room upon arrival, or book one with a pool, check your bags and go swim..

The pay lounge is too pricey. Just go to your hotel, drop off your stuff and start exploring. Go to a decent tea house and have a leisure dim sum breakfast to start.

It can get quite cold in the early AM for a swim if the OP is travelling in the winter months!

First off, try to get into your hotel early and if they can’t do that, at least drop off your bags.

One low energy activity I would suggest, particularly for your friend who has never been there before is a ride on the Star Ferry. You could get out and walk around on the other side or simply turn around and return to the Kowloon side.

In the general area of Tsim Sha Tsui, make your way to Kowloon Park for a leisurely stroll or simply find a place to sit and people watch. Right across from the park, inside the Miramar Shopping Center (on Nathan) is the Tsui Hang Village Cantonese restaurant. This is a large open room where the atmosphere is provided more by the staff and patrons and not the Spartan décor. It is a great introduction to Hong Kong dim sum. They open at 10 am on Sunday and 11:30 am other days.

There are several open markets in the same general area that you can turn into a self directed walking / metro / taxi tour. Depending on how tired you are, you can do one or all of these.
• About a 10 minute walk from Kowloon Park is the Jade Market.
• A bit further (take a cab or metro) is the Ladies Market
• Less than a 10 minutes walk from there is the Gold Fish market and
• Very close by to that is the Yuen Po Street Bird Garden. You’ll probably want to take a cab ride back.

We used Hong Kong as a stopping point on a trip to Bali a few years ago and did pretty much the market walk as described above and posted a report at: http://www.se-asiatravel.com/bali-2002/hong-kong/

bring a wet suit then for swimming

mediakzar, totally by chance, that's the restaurant where we had dinner the night we arrived in Hong Kong. We were staying at the Y and walked up Nathan Road. We saw the signs for the shopping center and thought we might find a food court, instead we found the restaurant you mentioned (I didn't know the name of the restaurant, just the shopping center, but I googled to see pictures). It was a great experience -- we were the only non-Chinese in the restaurant, the staff didn't speak English and we don't speak Cantonese, but we got along just fine with pictures. Well, sort of. One of the dishes we ordered caused the waitress to start giggling, and somehow she conveyed to us that we were ordering dessert to start our meal! The food was very good, and it's moderately priced.

Many thanks for the suggestions. I appreciate your taking the time to give inpur.

mediakzar and sf7307. The Tsui Hang Village Cantonese restaurant sounds fun. We will be staying in the area, and I'm glad to have this recommendation--whether we use it for our first morning or not. We will be in Hong Kong 5 full days.
Everyone--I'm thinking about the half day Hong Kong tour offered by several agencies. I'm a bit tired of it,having taken it at least three times, but I think for my friend it would be a good introduction to the city. Those tours usually provide a hotel pick-up between 8-9, and if we could get into the city in time to join one, that would take care of our first morning.
Our scheduled arrival on Cathay Pacific is 5:45. A faster option than an airport shuttle to the hotel would be a taxi, wouldn't it? Do you think we could make it to our hotel, not yet booked but it will be in Tsim Sha Tsui, in time to drop our luggage off at the hotel and then join the tour? Not sure how long it would take a taxi at this time in the morning.
Does anybody know off hand the approximate cost of a taxi? If not, there's sure to be something on that on the boards here, and I'll research.
If the tour activity isn't feasible time wise,
many thanks to all who've responded with other suggestions.

how about the hop on hop off bus tour, one on each side?

The Plaza Premium Lounge charges about $20 US for a shower. Some may feel this is too expensive but on two recent trips I arrived at HKG from the US around 6:00am, showered at the lounge, and then took the airport express to my hotel to drop off my bag. I felt refreshed and awake enough to spend the morning out in the city before checking in to the hotel after noon, so for me the shower was most definitely worth it.

I'm pretty sure there are other packages where you can stay at the lounge and nap or have breakfast.

I think it's unlikely a hotel in Hong Kong will allow you to check in early morning without extra charges.

@JohnH. Glad to hear that your experience with the Plaza Premium Lounge was positive. No matter how else we fill our time, this could be the best way to start our day.
@rhkkmk--the hop on and off bus would be a good option for a city introduction. I'm afraid the timing for the half day HK tour might be too tight.
Thanks, both of you

Taxi and Airport Express take about same time to get to a hotel in Tsim Sha Tsui. Taxi cost about HK$250.

I suggest against taking a tour or hop-on bus. Plenty of easy things to do in the morning after getting the dim sum breakfast. Flower and Bird Markets, and/or Wong Tai Sin and Chi Lin Nunnery/Nan Lian Gardens immediately come to mind.

did not suggest hop on bus for day 1, but for a later day

There was a time I had to go to HK frequently and with Cathy Pacific the arrival time was about 6am. The issue for me was to fight the fatique and remain relatively awake until bed time. I found No-Jet-Lag Homeopathic Remedy helpful in doing the job. You can find them in amazon.com and healthfood store for about $10. I promise I have no personal gain in this recommandation. Hope this helps.