Mr Clegg said the result of the election meant politicians had a "duty to speak to each other", as he arrived at a meeting of senior Lib Dems in central London.
Predicting that talks on forming a government could take days, Mr Clegg said he would make the case for four priorities - fairer taxes, changes to the education system to boost the chances of poorer pupils, a new approach to the economy and "fundamental" political reform.
"It is precisely those four changes which will guide us in the talks ahead," he said.
Mr Clegg arrived at the headquarters of the Local Government Association for discussions with his front bench team, which will be followed later by a meeting with all new Liberal Democrat MPs.
He will attempt to gain their backing for his negotiating strategy as he embarks on discussions with the Conservatives that could force Gordon Brown out of No 10.
Senior figures from the two parties met last night to begin talks on Tory leader David Cameron's "big, open and comprehensive" offer to work together in government after the General Election produced the first hung parliament in a generation.
Standing on the steps of Local Government House in Smith Square, Mr Clegg told waiting reporters: "Clearly, the result of the election means that politicians have a duty to speak to each other because people deserve good, stable government.
"That is why I am very keen that the Liberal Democrats should enter into any discussions with other parties, as we are doing, in a constructive spirit. That is precisely what we will do in the coming hours and days.
"Throughout, we will be very much making the case for the four big priorities that we have always said, well before this election took place, would guide us in any circumstances.
"They are there on the face of our manifesto:
"Firstly, fair tax reform; secondly, a new approach in education to provide the fair start that all children deserve in school; thirdly, a new approach to the economy so we can build a new economy from the rubble of the old; and fourthly, fundamental political reform of our political system.
"It is precisely those four changes which will guide us in the talks ahead."
There was an encouraging shout of "come on, Lib Dems" from a passer-by as Mr Clegg finished addressing journalists.
Several frontbenchers predicted an "interesting" day as they arrived to hear what their leader had to say.
Work and pensions spokesman Steve Webb said he did not know if there was support in the party for a deal with the Tories, adding: "One thing is that this has all moved so quickly."
Shadow Cabinet office minister Jenny Willott, meanwhile, said she was expecting a "very interesting debate".
And former leader Lord Ashdown of Norton-Sub-Hamdon urged reporters to be "a little bit patient" as the party considered its next move.
Culture Secretary Ben Bradshaw today insisted Gordon Brown could stay in No 10 in a "progressive" coalition deal with the Liberal Democrats, if their talks with the Tories failed.
He told BBC Radio 4's Today programme: "It would be inconceivable to me for the Liberal Democrats to sign up to anything that fell short of a guarantee of a referendum on reform of the voting system.
"I still see the possibility of a progressive coalition in this country."
Asked if that would be with Gordon Brown as Labour leader in No 10 Mr Bradshaw replied: "Yes, indeed. I think the fact that we have deprived the Conservatives of a majority is no small victory for Gordon Brown."
He went on: "We are in a new world. The people have spoken, the people have won this election, no political party has won this election. This is a very exciting moment for progressives."
Mr Bradshaw insisted: "The progressive parties in this country now have a huge majority and I hope that is the outcome."
Liberal Democrat rules impose a "triple lock" arrangement which ties Mr Clegg's hands in taking any step which could impact on the party's independence of political action - such as entering into a pact with the Tories or Labour.
He must first secure the support of a clear majority of Lib Dem MPs and federal executive members for any such agreement.
If he fails to achieve a three-quarters majority of each of these groups, he must call a special conference to approve the move before it goes ahead. And if he fails to get a two-thirds majority at the conference, the question goes out to a postal ballot of the entire party membership.
Meanwhile, Shadow defence secretary Liam Fox warned a government could not be "held to ransom" by the Lib Dems demanding proportional representation, when the issue had not featured prominently in the election campaign.
He said the Tories had won most seats and the most votes and had made clear in the campaign that "we were very much against it (PR)".
Dr Fox told Today: "What leaders will have to focus on is the fact that the Conservatives are the biggest party and it's reasonable that a programme would be followed that put the larger part of our manifesto into place.
"The question is, will the parties focus on the things they have in common and provide a stable government for the country or will the elements within the parties be allowed to focus on their differences and try to obstruct that process.
"What is important here is to have a change in mindset of the politicians. It's not a question of what we want, it's a question of what the voters decided."
Dr Fox warned the Lib Dems: "It would seem to me very strange in an election that was dominated by the economy...if the government of the UK was held to ransom over an issue that the voters did not see as their priority.
"I don't think that it's reasonable, given the result of the election, where we did come clearly ahead of any other party, that an agenda would be applied that was very much against what a very large proportion voted for."
He said that was not "a free-for-all for politicians cobbling deals after the election".
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