IF the British and Irish Lions are to win their three-Test series against the All Blacks, a host of individual things will have to go right for them. From each player getting the better of his opposite number - or at least as many players as possible doing so - to the avoidance of injury in the tour’s early games, so many factors will need to stack up in favour of Warren Gatland’s squad if they are to emerge victorious.

In the end, however, the outcome of the series may rest on a few simple principles. Get more than one or two wrong, and the Lions will have little chance of beating New Zealand. In fact even if they get them all right it could still be touch and go, but they will at least have given themselves the best possible chance.

1 Losing can be good for you

Not in the Tests, obviously. But there are six games on this tour before the first Test, beginning with a match against a Provincial Union 15 on Saturday. While the instinct of every coach and player is to want a 100 per cent record, Gatland should not be afraid to take risks in the build-up matches even if they harm the chances of winning an individual game.

The crucial thing, however, is drawing the correct lessons from a defeat. The classic example of this came on the 1997 tour to South Africa when the Lions went down 35-30 to Northern Transvaal - their only defeat before the series was won.

After some straightforward wins, the tourists were bullied up front by their first Super 12 opposition, and the result dispelled any remaining complacency. It also surely got rid of any notion that the front row for that game - Graham Rowntree, Mark Regan and Jason Leonard, all of England - would be good enough for the Tests. Sure enough, when the Lions met the Springboks for the first Test in Cape Town, the front row was Tom Smith of Scotland and Irish duo Keith Woods and Paul Wallace.

2 Don’t fight this tour with the tactics of the last one

There is always a temptation for coaches to go with what has worked for them before, be that individual players or whole game plans. “If it ain’t broke, don’t fix it” can be a decent rule of thumb, after all, but too often coaches persist with a winning formula when the circumstances have changed.

Thankfully, at least in terms of game plan, Gatland has given some encouraging signs that he will not persist with the so-called Warrenball strategy that has served him well in the past. Employing crash-ball centres may work against the Wallabies, but, while physical power will of course remain crucial, something more varied and unpredictable will be required against the All Blacks.

When it comes to over-reliance on players who have done a job for him in the past, by contrast, Gatland continues to cause concern. Of the original 41 men selected, 12 were from Wales: a worryingly large number given the principality’s indifferent form during the season.

3 Get your replacements strategy right

That group of 41 has, of course, already been changed. Scotland captain Greig Laidlaw joined compatriots Stuart Hogg and Tommy Seymour in the squad after England’s Ben Youngs withdrew for family reasons, while James Haskell has replaced England team-mate Billy Vunipola. More replacements will inevitably follow, and there is perhaps a danger that in each case Gatland will simply go for Option B, the first man in any given position on the reserves list, when a more radical change of plan might be better.

In the case of Vunipola, for example, Haskell’s admirers might argue that he is the closest thing available to the Saracens No 8. Conversely, there is a strong argument that there is no such thing as a Vunipola-light option, and that in the absence of the man himself a different back-row strategy should be sought. A strategy that involves Hamish Watson, for example.

4 Win the propaganda war

How not to go about this was demonstrated on the previous tour to New Zealand in 2005, when Sir Clive Woodward took spin doctor Alastair Campbell along to look after media relations and the attempt to control everything provoked annoyance on all sides. A more successful strategy was pursued way back in 1971 by head coach Carwyn James and tour manager Doug Smith. As detailed in a new book on that tour, When Lions Roared by Tom English and Peter Burns (Polaris, £17.99), James insisted in press conferences that there was a weak link in the All Blacks team, while Smith said there were “two fatal flaws” in New Zealand rugby that the Lions could exploit. They never identified the weak link or the flaws, provoking paranoia within the All Blacks camp.

5 Unity is strength

A truism more honoured in the breach than the observance by most teams, but one that it is crucial to get right when you are a squad on a long tour. The casting adrift of the midweek players in some Lions expeditions had a severely damaging effect on morale, and cannot be repeated this time round.

The key examples here are 1989 and 1993. After the first Test was lost to Australia in '89, the midweek team responded in the next match with an inspiring win over ACT and the tour got back on track, ending in a series win. Four years later in New Zealand, conversely, the dirt-trackers were demoralised and did nothing in the later matches to support the Test team, who lost the series.

6 Believe in yourselves

Again, an obvious one, but never more necessary than against the All Blacks, whose triumphs at the last World Cup have burnished their aura of invincibility. There is a significant role to be played here by those Irishmen who were on the winning side against New Zealand in Chicago last year, and more generally there is the need for at least one player to produce the sort of swagger that the great Barry John had in 1971.

“Don’t worry, boys,” the fly-half’s fellow-Welshman Mervyn Davies remembers him saying in When Lions Roared. “It’s only a game. Just give me the ball and I’ll win it for you. It’s only the All Blacks. How many points do you want me to score today?”

You need to be quite good to get away with that sort of statement, obviously. But then the Lions will need to be quite good to beat the world champions.