Launching a consultation on policies for the campaign, she said Labour had "wasted" 16 years of devolution.
But she would not say what price she would demand to share power with Labour, as Plaid did from 2007 to 2011.
Welsh Labour said the "tired attacks" were a "poor excuse for a campaign".
Speaking in Cardiff, Ms Wood said the four years of a Labour-Plaid coalition government were "a small beacon of hope in terms of a longer period of wasted opportunity".
Plaid wanted to be in charge of health and education "in particular", she said.
The party's education spokesman Simon Thomas said: "I don't think we will see any real change in Welsh politics until the hands of the Labour Party are off health and education."
Plaid Cymru is currently the third largest party in Cardiff Bay, with 11 of the 60 seats.
Ms Wood has already ruled out a deal with the Conservatives after the elections.
However, on the subject of coalitions, she said on Monday that people were "bored with that kind of conversation".
Ms Wood added that her party would be concentrating on their own policies "rather than constantly obsessing with which party will do deals with which party".
A Welsh Labour spokesman said Ms Wood's comments were "completely out of step with people's own experiences".
"Only Welsh Labour will take on the Tories," the spokesman added.
"It is telling that Plaid Cymru yet again seem unable or unwilling to take on the party that has slashed Wales' funding and attacked our most vulnerable communities.
"Wales won't forget that Plaid Cymru have tried before to get the Tories into power in the assembly," referring to talks in 2007 about a so-called "rainbow coalition" deal which would have excluded Labour from government.
For the Conservatives, Welsh Secretary Stephen Crabb called on the opposition parties to "think the unthinkable and look at the options that provide this country with an alternative to the Labour Party".
When asked how realistic it was for Ms Wood to work with Welsh Tory Leader Andrew RT Davies to make this happen, he told BBC Radio Wales it would be "difficult, challenging but I would never say it's impossible".

The star told a Cannes press conference she likes to make "bold" choices, as if she were at the start of her career.
Kidman said while she doesn't have to work, she does so because of her passion for cinema.
The star of The Killing of the Sacred Deer, in competition at Cannes, said her young children will be banned from seeing the dark psychological thriller.
Kidman has two grown-up children from her marriage to Tom Cruise and two younger daughters with her current husband singer Keith Urban.
"My (younger) children have very little understanding of what me or my husband do. Their lives are obviously far more important!"
She added: "I'm at that stage in my life where I still try to act as if I'm 21 and starting my career.
"At this stage of my life, I'm just trying to stay very bold and open and try things and support film-makers I believe in."
The Killing of the Sacred Deer features an eminent surgeon Steven Murphy - played by Colin Farrell -  who adopts a teenager into his family. Things start to go horribly wrong when the boy turns against Murphy.
Kidman plays ophthalmologist Anna Murphy, who is married to Steven.
It's directed by Yorgos Lanthimos, the Greek filmmaker behind indie hit The Lobster, which won the Jury Prize at Cannes two years ago. Farrell also starred in that film.
Kidman said she was "hypnotised" by Lanthimos' script.
She has four projects showing at the festival this year, but said: "That's a confluence of events - that's not something I was aware would be happening."
Her other Cannes showings are in The Beguiled and How to Talk to Girls at Parties, as well as the second series of TV drama Top of the Lake, from Jane Campion.
She singled out Campion for praise, saying she had been a friend of hers since the age of 14 and that "she discovered me, basically."
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Plaid Cymru leader Leanne Wood has said her party wants to deprive Labour of control of health and education policy after the 2016 assembly election.
[NEXT_CONCEPT]
Oscar winner Nicole Kidman says she still acts like she's 21 when it comes to acting roles.