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".
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.