EDIT: This post has been moved from from the "Introduce Yourself" area as it's more appropriate here.
If you've got a trailer, try the northern Norfolk Broads. There's plenty of room to experiment and not much tide. You'll need a short stay licence from the Broads Authority, and it's best to avoid the school holidays.
Note that I've moved this topic to "Help Desk" as we've moved away from basic introductions
I don't think you can do better than the Parish Staithe at Hickling. It was around a fiver the last time I did a launch and recovery there and is less than 100yds from Hickling Broad. At the end of the dyke with the slipway, stop to hoist at the Pleasure Boat Inn moorings. And once on the Broad, Norfolk's largest, there's plenty of space to practice tacking before you have to put the training into practice in a narrow river.
The Slipway - Launch and Recovery page shows me at the Parish moorings. The slipway in the photos is now reserved for locals and can only be used from their dry berths. However, opposite is now a similar slipway with winch that can be used by the public. It's just visible in a couple of the pictures.
Being above Potter Heigham Bridge, Hickling is an area free of the largest hire boats so provides much less stressful sailing for a beginner as encountering drunken land lubbers in over-sized boats at close quarters with no understanding of how a sailing boat works and why it might have to make a 90° turn right NOW is much less likely.
The only possible disadvantage of starting from Hickling is that you might encounter me playing in the Muddy Broad Blues Band if you take an apres-sail drink or bite to eat at the Pleasure Boat.
If that is too daunting a prospect then try the slipway at the Martham Boating Building and Development Company. It's on the other side of the broad and will almost inevitably force you into tacking beofre you reach an open broad.
I agree with Greg about Hickling being the best place. You can get from there to Horsey Mere as well, another nice big broad. Don't be tempted to try and go through Yarmouth like they do in the Arthur Ransome books. The southern broads are much less yacht-friendly to sail on - more tide and less open water - and crossing Breydon Water is definitely not for our size of boat, even though I know someone who's done it several times in a yacht without any kind of engine. The other parts of the northern Broads are well worth visiting though, particularly the Barton Broad area.
Don't be tempted to try and go through Yarmouth like they do in the Arthur Ransome books. The southern broads are much less yacht-friendly to sail on - more tide and less open water - and crossing Breydon Water is definitely not for our size of boat, even though I know someone who's done it several times in a yacht without any kind of engine. The other parts of the northern Broads are well worth visiting though, particularly the Barton Broad area.
Certainly, the Northern rivers are prettier but that is why they are so much busier. That, in itself, can have disadvantages in high season, especially for a novice sailor.
It takes some skill to sail, rather than use a motor, on some of the narrower or tree-lined stretches, such as parts of Fleet Dyke, Ranworth Dyke and the River Ant. Even the relatively wide Bure through Horning can be a real struggle given the level of traffic you can experience. The wash from other boats and the fluky winds because the SeaHawk's mast doesn't rise above tree level can take some skill to master and progress can be frustratingly slow. But all these issues fall away if you are prepared to use a motor.
On the other hand, providing you are prepared to cope with the tides, and have a standard 4hp engine in reserve, the tides should not be something to worry unduly about - they just effect journey times to your planned mooring - and, by and large, the much wider and less busy rivers can make for much easier river sailing. Key tip: Watch the burgee to determine where to head not some landmark on the far bank as you came about.
However, I would agree that tackling Breydon is not for a novice single-handed, but it is most certainly do-able with experienced crew and it's always been something I wanted to tackle single-handed on Just 17 but never found the time. I did it, with crew, on my father's boat, as reported on my GregAfloat site in Aboard Jemima - 1976.