Kirsty Williams said the Lib Dem vision for May's assembly election would be to "provide good schools, good hospitals and a vibrant economy".
Ms Williams will accuse Labour Welsh ministers of failing "to get even the basics right" after 17 years in power.
The conference takes place on Saturday and Sunday.
"In the forthcoming election, the Welsh Liberal Democrats will show that we have listened to people's concerns," Ms Williams said.
"Our vision for a future Welsh parliament is one that finally gives people what they want - good schools, good hospitals and a vibrant economy.
"We will be relentlessly focused on getting public services right."
The party's key pledges include:
The Lib Dems are facing an uphill struggle in the assembly poll, after their collapse at the 2015 general election which left them with just one MP in Wales.
They currently have five assembly members.
Before Ms Williams' main speech on Saturday, party members will hear from UK Liberal Democrat leader Tim Farron.
It's almost a cliche these days to describe an election as being a "make or break" one for the Liberal Democrats, but with the party facing a possible wipe-out in May's assembly election it's clear a bad result could cause long-lasting damage.
Having seen its Westminster representation reduced to a single seat and its local government base severely eroded, the Welsh party has come to depend more on the assembly group to maintain its profile.
The last assembly election in 2011 saw a plunge in support for the party following the formation of the Conservative-Liberal Democrat coalition at Westminster.
But despite a near-collapse in its vote, the party succeeded in dodging the bullet in terms of seats, retaining seats by narrow margins in four of the assembly's five electoral regions.
The emergence of UKIP as a major electoral force in Wales will make retaining those seats far harder in 2016 and the party probably needs a substantial increase in its support just to stand still.
Quite where those extra votes might come from is anyone's guess.
The Welsh Liberal Democrats' leader has pledged to be "relentlessly focused on getting public services right", ahead of their spring conference in Cardiff.