It is worth knowing some of the secrets of the Tube, particularly if you will be in the very busy Covent Garden area (which part of the area, by the way?).
There are tricks which can save you plenty of time.
The Tube map is not representative of actual distance, nor of actual compass direction.
The shortest distance between any two stations is the very close Covent Garden and Leicester Square. So in the Covent Garden area not only do you have the Piccadilly Line but also easy access to the Northern Line (Charing Cross Branch). If you are connecting between the two it is often quicker and easier to walk between them than try under ground. Enjoy the high speed lifts at Covent Garden, and be aware that in times of crowding Covent Garden may close.
A great way to save time is to avoid making changes at Bank. The station is a real maze and huge. Change elsewhere.
At certain stations there are very easy same platform or cross platform connections between lines.
Oxford Circus - cross platform interchange between Bakerloo line northbound and Victoria line northbound and between Bakerloo line southbound and Victoria line southbound.
On the north side of the circle the Hammersmith and City, the Metropolitan, and the Circle lines all share the same platforms (except at Baker Street and Paddington) so changes between are trivial. On the south side of the circle, the District Line and the Circle Line share platforms so again changes are so easy.
At Baker Street across platform change between the Jubilee line and the southbound Bakerloo line.
Barons Court is a great cross platform place to change between same direction trains on Piccadilly Line and the District Line if, for example, you are going between Heathrow and the Victoria station area or anywhere in The City (financial area) or around the Tower of London.
Euston (not Euston Square) is good for same direction changes between the Northern Line (Bank Branch) and Victoria Line. Note - this is not true for easy connections between the Northern Line (Charing Cross Branch) and the Victoria Line. If you are in the Covent Garden area you will be near the Northern Line (Charing Cross Branch) but not near the Northern Line (Bank Branch). Look at the Tube map - it will become clear
Be aware that although there is a Tube sign on Russell Square, the entrance is down a side road and not on Russell Square.
Finchley Road is another helpful station - cross platform interchange between Jubilee line northbound and Metropolitan line northbound and between Jubilee line southbound and Metropolitan line southbound.
And last but definitely not least - Green Park looks to be a logical interchange between the Victoria, Piccadilly, and Jubilee lines. But if you follow the signs from the platforms to the one you want you will be taken a long way around with lots of short staircases. Much faster and much easier is to take the escalator straight up to the booking hall, then down the escalator to the line you want. (thanks so much initially to former poster here and London resident, Emma - we miss you Emma - who mentioned this trick the first time).