The Fianna Fáil leader will be selecting coalition partners based on who he thinks has the "backbone" to stay in government for a full term.
Micheál Martin has warned that previous negotiations took too long and some who engaged in discussions were not serious.
However, he said he does not believe there will be a government in place before Christmas.
"A lot depends on the characters of those who are supporting you, people who can take the rough with the smooth and have the backbone to see it through.
"Numbers is one aspect of it, but the degree of commitment that individuals can give to the government is another.
"Last time out not everybody was as anxious to get into government as they might have proclaimed, and government can be a challenging place to be.
"So we just want to test the waters and see what others are saying," he told reporters in Farmleigh House after a meeting of the British Irish Intergovernmental Conference.
Both the Fianna Fáil and Fine Gael parliamentary parties will meet separately on Wednesday to discuss coalition options, with Mr Martin saying he will be seeking mandate from his colleagues on the direction of discussions.
Mr Martin suggested that the legalisation of drugs such as cannabis which had been in the Fianna Fáil manifesto, will be a policy he will be pursuing in programme for government talks.
During the election campaign, Taoiseach Simon Harris ruled out such a move.
However, when asked about key policy red lines including drugs, Mr Martin said: "My understanding is quite a number of Fine Gael political representatives are not that much against the specifics of that, and there was an all-party Oireachtas report from the last Dáil, which forms the basis of progress on that. These are issues we can discuss."
He added he will be looking to form a government that is pro-enterprise and pro-European Union and that has a focus on facilitating home ownership and investing in public services.
Mr Martin would not be drawn on the issue of a rotating Taoiseach and whether Fine Gael should have a shorter time at the head of government given the fact that the party has come back with 10 fewer seats than Fianna Fáil.
Justice Minister and Fine Gael member Helen McEntee said disability services, housing targets, and supporting business will be key elements for her party in any discussions.
"It's important that we engage and that we take on board everybody's views, but our focus is on policy.
"What I saw the last number of years with the government just gone, is that because we had a very strong policy document, a very strong programme for government in place, when bumps arise, as they always do if there's more than one party in government, you have a strong document to work off, which provides the stability that we've had over the last number of years."