If you’ve recently become an entrepreneur, consultant or self-employed person: Welcome to the world of quarterly taxes. While tax day stories typically focus on getting through last year’s filings, even harder, for the surging number of people affected, is figuring out what to pay for the first quarter, due at the same time.

Guess too low, and you’ll owe penalties. Guess too high, and you’ll have less cash to spend during the year. But guessing just right means estimating your income, and your business expenses, for the year. And that’s no easy task.

It’s the simplest things that can trip you up at tax time, like not getting money into your account or forgetting to sign your return. But this year, with so many tax changes, there are even more minefields.

If you were thinking you’d do your tax return the old-fashioned way, by hand, just stop now. Get an accountant or a tax-software program. Without software — which, yes, even accountants use — you’ll be unlikely to get through your return without errors.

There’s just two weeks to go till tax time, and Bill Fleming, managing director in the personal financial services division of PricewaterhouseCoopers, has been cranking hard on his clients’ returns, but has yet to start the one he’ll file for himself and his wife. “I know all about procrastination,” he laughs.

If you haven’t finished your taxes — and fear waiting in line at the post office on April 18th — you’re not alone. In fact, this year tax season may be moving a bit slower than usual because the last-minute, year-end tax agreement delayed the usual timetable for the Internal Revenue Service to get its forms and systems ready. “We are probably a week behind last year,” Fleming says. “Everything has been pushed back a week or so.”

Giving money away has such an emotional component to it that it’s hard, sometimes, to think about in strategic terms. But the truth is that if you pay as much attention to your giving strategy as to your investing one, you can have more impact and fund more of the organizations you care about without getting sidetracked by requests.

Tom Tierney, chairman of the Bridgespan Group, which advises both philanthropists and nonprofits, and co-author of the forthcoming book Give Smart: Philanthropy That Gets Result, has been thinking about how to make your philanthropy count for a long time. Before co-founding Bridgespan in 1999, Tierney, who has an MBA from Harvard, had been chief executive of Bain & Co. But as he reached his mid-40s, he made a career shift that few on Wall Street understood at the time. “Midway through the ’90s, I started asking, ‘Are there other ways to live my life?’ ” he recalls. “I had a couple of senior partners come into my office and shut the door, and say, ‘are you okay?’ They were expecting me to say I had gotten bad news from the doctor.”

There’s one thing you really need to know about the new rules on cost basis: If you haven’t had a conversation with your broker about how you want your basis to be calculated, it’s time.

Cost basis is one of those topics that make all but the most hardy investors roll their eyes or go completely blank. And with good reason: It’s stupidly complicated. Not only is the cost basis itself difficult to figure out (what with splits and spinoffs and multiple purchase dates), but the tax code lets you choose among different ways of calculating cost basis that vary depending on if the security is a stock or a fund. Figuring out whether to do first-in, first-out, or specific-share identification, is enough to make your head spin, yet the amount of tax that you owe can vary wildly depending which method you choose, especially if you’ve been buying regularly over the years at different prices.

For those whose loved ones died in 2010, this is the time to wrap up their estates.  Last year was an unusual year — the estate tax disappeared altogether to the benefit of some and the detriment of others. But in its absence, a different capital gains tax emerged. That means anyone sorting out a 2010 estate now gets to choose which tax to pay.

The choices are to pay the estate tax under its new rules, which allows for a $5 million exemption and a maximum tax rate of 35 percent, or to opt out of the estate tax and elect what’s known as “carryover basis.”  The answer you might think — to opt out of the estate tax — is likely the poor choice for the vast majority of people.

It’s hardly a secret that state budgets are tight. Still, when budgetarily-beleaguered Illinois raised its individual income tax rate to 5 percent from 3 percent, it raised eyebrows — and questions about what other states might follow.

The Tax Foundation, in a recent research report, notes that fewer states raised taxes in 2010 than had been expected to do so, but that with the temporary federal stimulus aid ending mid-year and many states in budgetary trouble, “2011 may be a year of dramatic tax increases.”

Since 2006, a popular tax rule had permitted those aged 70-and-a-half or older to donate up to $100,000 from their Individual Retirement Accounts to charity. Last year, as the tax flux dragged on, no one knew whether this provision would stay or go.

At the 11th hour, the December tax legislation gave it the okay: The provision was both extended through the end of 2011 and permitted retroactively for 2010. Given the delays, the deadline to do this and have it count for 2010 has been pushed out till Jan. 31. If you’ve got the funds and it makes financial sense, you could make two IRA-to-charity rollovers this year, counting one donation for 2010 and one for 2011.

It was a perhaps inevitable problem after the market downturn: Charitable trusts that are underwater.

Charitable remainder trusts, or CRTs, are typically used by wealthy people who want to give a seven-figure gift to charity, and still retain an interest in the donation. They work like this: First, the donor puts the asset into a trust for charity. Then, the donor gets the income from the trust, and a charitable donation for tax purposes. At the end of the trust’s term, the asset (that is, the “remainder”) goes to charity.