Any advice for starting lane swimming?

Swimming is great exercise and its gentle on the body, so it should take a lot of the impact and pressure off your ankles and knees.
When I go to my pool for some lane swimming I usually start off next to a lane so that I can still be guided by the ropes, then move into a lane once I've warmed up a bit. Start off slow and judge which lane suits you best. I don't see any problem with changing lanes if you want to change your pace, although in my pool its usually pretty quiet around lunchtime (I go on a weekday) so I don't usually need to change lanes unless it starts getting busier.
I find that swimming definitely gets my heart-rate up, but I also find it easier to maintain my pace than I would if I was walking/jogging etc.

Hope it works well for you Good luck, and have fun!

Swimming would be good.

I might suggest you try lifting for your knees and ankles. It will strengthen them tremendously and is a lot easier on your joints than 30DS.

Between lifting and running with proper form in both I was able to cripple a cane that was the only way I could get around.

Unfortunately me and my mum can no longer afford our gym membership, I've been walking briskly and using videos like 30 Day Shred, but I'd like to add an hour of swimming to that since it's the only sport I could ever do!

My local pool does lane swimming with slow, medium and fast lanes for an hour at lunch time.

Should I switch between the lanes to vary my heart rate? Will I be able to get a good calorie burn out of a brisk swim? My knees and ankles hurt when doing 30 Day Shred, will swimming be good for that since there's no weight on them?

Any other advice? Thank you in advance!

Great choice! Year-round swimming was my first sport :-) As LouSmorals points out, it really is that simple. So please *do* go hop into the pool!

Now I'll get into the weeds, just as context (since you're asking about details). I don't know your specific pool, but here are a couple of general etiquette notes from the hundred or so I've swum in:

1. Usually you stay in one lane for your whole workout, unless you find you've accidentally misjudged the speed of the other swimmers. It is *unlikely* anyone would say anything to you if you switched, but it's slightly disruptive, even if you time it properly to avoid messing up someone's turns. Again, NOT a huge deal, and everyone understands it sometimes takes a few tries to find the right spot when you're starting :-)

Pick the lane where you will spend the least amount of time passing other swimmers. AND where other swimmers will spend the least time passing you. Many swimmers spend at least part of their workout doing sprints or using a kickboard or pullfloat, btw, so it isn't weird to change up your pace during your workout.

2. When you're on the wall, scoot to the side so that others can flip turn or push off to start their set - a small courtesy that goes a long way to preventing traffic jams! This also lets people rest between sprints without interfering with someone swimming steady laps.

3. Once you're comfortable getting into the water and doing your laps, consider looking up some swim workouts online. They help break up the time/yardage into smaller chunks that can make it more interesting. One of my favorites is called "The Zen Mile" and it helps keep me from getting discouraged when I'm not in shape to do an aggressive competitive workout or even maintain a steady pace for more than 200 yards.

The water is AWESOME. Yes, you can get a GREAT workout, and I often think that emerging from the water may have been our dodgiest evolutionary move as a species.

Please PM me if you ever have pool or open water questions. Amphibians are friendly people :-)

P.S. Do some laps with the kickboard if you want to work on your ankle strength. Add the little "Zoomer" fins for extra challenge down the road!

There is a certain etiquette for lane swimming. Mainly, know your speed and be in the correct lane. If you see that everyone is passing you, simply move to the slower lane.

Also, don't take up the entire lane, stay to the right. People swim and at the end of lane will turn around and come back on your left. Sortof in a big flattened counter-clockwise circle.

If you feel someone tap your ankle, they are trying to pass you. Try so scoot to the right a bit more to let them by.

If you take a break at the end of the lane, try to stay out of the way of people coming in to turn around, you don't want to get kicked when they do their turn!

Hopefully this helps you a little in your swimming. It's fantastic exercise and is really great over all!

I swim. I love swimming, I am joining a masters swim club this week to help me improve my endurance.

I agree with other commenters on the etiquette required.
The fast, medium, slow lanes are set by how fast you can swim a lane going normal front crawl for example.

I go swimming with a friend so we usually share a lane, I have to wait until she nearly reaches the end before I start since I am a faster and more efficient swimmer then her, but she has the better endurance and it keeps me going.
I also go in the morning with a coworker who has been training for years. I lost count the one day after he passed me at least 10 times.

Look at using those free weights at home for some exercises.