By Vipal Monga and Emily Chasan

The end to a busy proxy season doesn’t mean corporate boards are off the hook. Hoping to avoid a poor showing in next year’s corporate-governance votes, companies already are reaching out to their largest shareholders in what has become a year-round campaign.

Shareholders, meanwhile, are finding they have more clout, as so-called say-on-pay votes and successful proposals by shareholders to nominate their own candidates for corporate boards force companies to pay more attention to their demands.

The proxy season, when most companies hold their annual shareholder meetings, extends from April through July. This year’s was marked by a resurgence of proposals urging companies to separate the roles of chief executive and chairman, according to data from investor-communications company Broadridge Financial Solutions.

Shareholders also were successful in pushing boards to remove takeover protections, but made less headway in forcing companies to disclose political contributions.

The biggest challenges for companies, however, were the nonbinding say-on-pay votes, which let shareholders weigh in on executive-pay practices, and “proxy access” requests, in which shareholders seek the right to nominate their own board-of-directors candidates.

At pension-fund giant TIAA-CREF, which oversees $486 billion in assets, representatives of as many as five companies a week are coming in to talk about their compensation packages and other corporate-governance issues, says Jonathan Feigelson, general counsel and head of corporate governance.

In the season that just ended, he says, the fund’s managers spoke with roughly 450 companies individually, up from about 400 in 2011, and most of them wanted to discuss executive pay. Say-on-pay votes are “creating an environment in which management and directors are becoming more willing to speak to shareholders,” he adds.

Other major investors have had similar experiences. The California State Teachers’ Retirement System, a state pension fund with $152 billion in assets under management, has spoken with more than 100 companies this year, particularly those it didn’t support in say-on-pay votes, says Aeisha Mastagni, investment officer at the fund.

According to law firm Sullivan & Cromwell, 53 companies lost say-on-pay votes this year. Although that represented only 2.4% of all such votes taken this year, the percentage was up from 1.3% in 2011.

Among the companies whose pay practices failed to win support from a majority of shareholders were Citigroup Inc., Chesapeake Energy Corp. and Nabors Industries Ltd.

In an April vote, 55% of Citigroup’s shareholders voted against CEO Vikram’s Pandit’s $14.9 million pay package. The loss prompted the big bank to step up its efforts to placate investors. Citigroup hired executive-compensation firm Frederic W. Cook & Co. to advise it on a review of its executive pay. A Citigroup spokeswoman added that the board’s compensation committee members “have been meeting with representative shareholders to fully understand their concerns.”

Paul Hodgson, chief research analyst for governance firm GMI Ratings, says that companies realized last year that they had to court shareholders after failing say-on-pay votes, and have beefed up their efforts.

He says Hewlett-Packard Co., reacted to a 2011 loss on say-on-pay by tying compensation for its new CEO, Meg Whitman, more closely to the company’s performance. The technology company hired Ms. Whitman last fall for just $1 in annual salary, but she was awarded H-P stock options worth more than $16 million, allowing her to reap large rewards if the stock rises.

H-P declined to comment.

“Companies have tried to address shareholder concerns honestly, and to a fairly large degree,” says Mr. Hodgson.

Shareholders were able to put proxy-access proposals on corporate ballots this year, subject to Securities and Exchange Commission approval, after a U.S. appeals court last year rejected proposed SEC rules that would have allowed big shareholders to nominate corporate directors directly.

Companies got at least 20 such proposals, but only nine of them came up for a vote, according to Broadridge. The SEC kept the others off the ballot due to technicalities. But shareholders won proxy access at Nabors and Chesapeake, which both also lost say-on-pay votes.

Chesapeake has stepped up its outreach efforts, and “is reviewing the overall compensation structure,” of the company says spokesman Michael Kehs. Nabors didn’t return calls seeking comment.

Patrick McGurn, special counsel at Institutional Shareholder Services, says shareholders are learning how to structure their proxy-access proposals so they aren’t disqualified by the SEC, which should increase the odds that more of them will reach shareholders for a vote in 2013.