You need to keep active, each and every day.  There's no way around this.  If you want to become fit you need to have a regular regime of activity.

Of course it doesn't have to be the same thing each day - and indeed there are good reasons for not taking up the same activity every day.  

Activity is good, but no activity strengthens every muscle, gets the heart rate up to the right amount, stretches the back just the right amount. 

But on the other hand you may be restricted somewhat by age, by past injuries, and simply by what you enjoy doing, and what facilities are available in your area.

The most important point is that you do not push yourself too far too fast.  Quite obviously if you have been doing virtually no exercise there is no point starting with a one mile run or a 50 length swim.  Even if you do manage to make it, you will be so exhausted  you won't feel like doing any exercise the following day.

So here are the key rules for starting off your activities:

1.  Take into account what you normally do, and just do a little more
2.  Plan to take some activity each and every day - it doesn't have to be the same activity every day, but you should aim to be doing something each and every day of the week.
3.  Try and build variety into your activity, so that you are doing different things on different days
4.  Activity should be enjoyable.  OK, you are trying to push your body, but even so, if you can make the activity enjoyable you are more likely to do it.
5.  If at all possible make some of your physical activity communal - do not get into the habit of everything being something you do on your own. 
6.  Don't start by going off and joining a gym, unless you are already very active.  Gyms can be good, but unless you are already active you will only be using a fraction of the resources of the gym - but paying for a lot more.   This advice is similar to our suggestion about not going out and buying special clothes.  Yes you need a swim suit if you want to swim, and you need suitable shoes if you are walking or running, but don't go mad.  Buying the clothes simply spends money.  It does not make you fit.

So what activities might you try?   Here are a few suggestions:

1.  Gardening
2.  Dancing
3.  Running
4.  Walking
5.  Badmington
6.  Cycling
7.  Swimming
8.  Tennis
9.  Table tennis
10.  5 a side football

This is of course a very abbreviated list - a list that you can indeed expand greatly.  But the list has a point because it has shows the variety that is available. 

Each of these areas has many options and possibilities.  Gardening might involve a gentle bit of weeding, or pruning the roses.  Dancing might involve jiving or the more sedate ballroom activities.   Walking can involve walking along the street to the supermarket instead of taking the car, or it can involve walking across a rural area.

And so on.  You have to choose the activity, or better still activities that you are going to undertake, and start exploring them. 

Finally, as we have said, a little more activity every day is a good idea.   But don't try and go too far too fast.

And a final word of warning: don't reward your activity by eating or drinking more than you would normally do (except of course, increasing the intake of water).

Set out your timetable, stick to it, and then extend it...