Tall and like football? Go and play centre-back. Enjoy rugby union and have a bit of pace? Winger.
Step forward Somerset's Dom Bess, who took 6-28 on his County Championship debut on Tuesday.
How did he come to bowl off-spin?
"I was always a little porker when I was younger, so I never took the long run-up," he said.
"I always took five or six steps and just trotted in."
Bess now has the best figures by a Somerset debutant for 55 years, since Tony Pearson returned 7-63 against Worcestershire in 1961, according to the Guardian.
But any 'puppy fat' the 19-year-old may have had has long gone, with the help of strength and conditioning coach Darren Veness.
"I met Daz and he made me run a lot, which I'm grateful for now," Bess told BBC Radio Bristol.
"Ask Daz about me, I was always a porker."
Just a month ago Bess, from Sidmouth, was taking 6-65 for Devon in the Minor Counties Championship as they lost to bottom-of-the-table Oxfordshire.
At Taunton, however, his victims included Ian Bell and Jonathan Trott, who have played a combined total of 170 Tests for England.
His family have a strong presence in the sport, with cousins Zac and Josh also representing Devon, but who was at the County Ground to watch his moment of glory?
"Dad was on holiday and mum was working, so I just had my girlfriend, her parents and a couple of my mates (watching)," he said.
"I think dad will be a bit disappointed - he's gone to Greece, somewhere like that, for a week away."

Shankaracharya Swaroopanand's comments came two days after the Shani Shingnapur temple in Maharashtra state let women into the inner sanctum.
For centuries, the temple had been open only to men.
Last month, the Mumbai high court affirmed the right of women to enter and pray inside all temples.
Women's activists had led protests demanding entry specifically to the Lord Shani shrine.
"Women entered Shani temple's inner sanctum," news agency ANI quoted the 94-year-old as saying on Monday.
"The women are worshipping Shani in the temple. By doing so, Shani's eyes would fall on women and this would result in increase of rape incidents."
Women were kept out of the Shani Shingnapur temple for nearly 400 years and temple officials, in the past, had claimed that the ban was actually "to protect women since Shani emits radiation which can harm them and cause deformity in a foetus if a pregnant woman enters the temple".
Last year, temple priests carried out an elaborate ritual cleansing after a woman managed to gain entry inside and offer prayers.
The temple authorities relented after last month's Mumbai high court ruling that women had a fundamental right to enter temples, and said those trying to prevent them would be handed a six-month jail term.
Several temples in India preserve the tradition of barring entry to women and in recent months, courts have been considering legal challenges to the policy.
Shankaracharya Swaroopanand's statement has caused outrage in India with many taking to social media to criticise him:
There were a few messages of support too:
Whether it comes down to skill level, body shape, or pure accident, anyone who has played a sport will have some memory of how they came to be given a particular role.
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A Hindu religious leader's comment that allowing women into a shrine devoted to Lord Shani (Saturn) will increase rapes has drawn criticism.