The booklet warns parents to look for changes in children's appearance
Parents are being given guidance on how to recognise signs their child may be in a gang.
The advice booklet coincides with the launch of a charity in Birmingham set up by the mothers of two teenagers who were killed in a drive-by shooting.
The home secretary said parents needed to know the signs of gang involvement and where to turn if they were worried.
But youth worker Shaun Bailey said by the time there were visible signs of membership it was "way, way too late".
The guide has been produced by the Home Office in conjunction with police, local authorities, parenting organisations and community groups including Mothers Against Violence.
The booklet says young people join gangs for a host of reasons including excitement, protection or money from crime.
It tells parents to talk to their children about "the dangers and consequences of gang involvement" and offer them more positive activities to get involved in.
Parents should also look out for certain changes in behaviour, including:
- Has your child started to use new slang words?
- Do they have any unexplained money or new possessions?
- Do they have a new nickname?
- Has their appearance changed? Are they dressing in a particular style or "uniform", for example, wearing a bandana?
- Do they use graffiti style "tags" on possessions such as schoolbooks?
- Do they have unexplained physical injuries?
The guide also gives parents some advice on what to do if their child is already involved in a gang, such as seeking help from local youth organisations.
"It's important to be clear that your child does have a choice, even when they think they may not," it says.
The guide's release coincides with the launch of the New Year Shooting Memorial Trust, set up by Beverley Thomas and Marcia Shakespeare.
Their daughters, Charlene Ellis, 18, and Letisha Shakespeare, 17, were killed in a botched gang attack outside a party in 2003.
The trust will offer support to families and young people affected by violent crime as well as preventative measures including help with employment.
Ms Thomas said: "Basically what the book is saying and what I would say - look out for certain signs of a child being active in a gang."
She pointed to such behaviour as getting home late from school, spending more money and adorning school books with "street name" nicknames.
Home Secretary Jacqui Smith said: "All parents worry about keeping their children safe - and need support to help them to do it.
"They need to know how to spot if their child is involved in a gang and where to turn if they are concerned."
'Stay a child'
But youth worker Shaun Bailey told the BBC News website: "I don't want to sound too critical because you have to respond somehow, but if you're at the stage when you're spotting these signs it's way, way too late.
"Only parents who have very strong relationships with their kids can step in then. Of course, some parents do, so it's worth saying, but not all.
"The other thing is that writing things down like this solidifies the existence of gangs. But gangs don't exist in a solid, regimented, uniformed way, they're much more fluid.
"Membership is based on personal relations - family, friends, the people you live beside - not some middle class notion of a uniform."
Mr Bailey, who runs youth organisation My Generation and is also Conservative prospective parliamentary candidate for Hammersmith, said prevention was key.
"The best way to keep your kid out of a gang is to keep your child a child.
"If you've got an 11-year-old being drawn into a gang they are upping their level of sophistication, losing their innocence, being 'cool'.
"What defends children from that is not being cool, and the best defence against being cool is being a child.
"So, do you talk to your kid? Do you know where they are? Do they have to come straight home after school? It's those things that really matter."
The Gangs: You and Your Child booklet is available at www.direct.gov.uk and 30,000 copies are initially being distributed in London, Liverpool, Manchester and Birmingham.