LONDON -- The FTSE 100 (INDEX: ^FTSE) has had a pretty erratic April, with some strong company results spurring it on while euro-fears and the dreaded "double dip" hold it back.

Reaching a high point of 5,875 early in the month, it once again scraped against that psychologically important but otherwise meaningless 6,000 level, only to fall back to a low of 5,596 and then creep slowly back to where it started. It looks likely to end the month around 5,780, and if you had stopped watching in-between, you'd have thought nothing had happened.

And in a way, nothing has, because these day-to-day movements don't mean anything to long-term shareholders, except that downward dips can provide us with buying opportunities.

And again the Fools' writers have unearthed a number of possibilities for you.

1. GlaxoSmithKline
The pharmaceuticals giant GlaxoSmithKline (NYSE: GSK) got the nod from two of our writers this month, with Prabhat Sakya pointing out that it "has already passed the worst of the patent cliff" and getting excited about the company's future drugs pipeline. And Cliff D'Arcy likes the well-covered 5.1% dividend yield, which beats the FTSE 100 average by more than a third -- and he says he'd be happy to add to his holdings at current prices.

2. Vodafone
With its consistently high dividend, it's hard not to like Vodafone (NYSE: VOD), and after the communications group finally went public with a 38 pence-per-share offer for Cable and Wireless Worldwide, Roland Head has been subjecting it to some scrutiny. He's in no doubt of his opinion that "Vodafone makes an excellent long-term buy for investors -- a decision made even simpler by Vodafone's tasty 5.9% dividend yield."

3. Royal Dutch Shell
Many investors would see a big oil company as an important cornerstone for a sound long-term portfolio, with an abundant supply of energy being required by every other industry on the planet. And after Royal Dutch Shell (NYSE: RDS-A) released forecast-beating first-quarter figures this month, G. A. Chester was moved to opine that both it and BP (NYSE: BP) are good values right now, especially for income seekers.

4. JD Sports Fashion
JD Sports Fashion has done rather well in recent years, and it has seen its annual turnover top 1 billion for the first time in 2012. With strong cash generation and a dividend hike of 10%, Cliff D'Arcy believes the firm's strong balance sheet, quality management, and future expansion plans mean the shares are rated too cheaply, saying, "For value investors, it may well be the strongest buy on the high street right now!"

5. Halfords
The high-street purveyor of bikes and car parts has seen its share price slump over the past couple of years, hit by the fall in discretionary spending. But on the occasion of Halfords' pre-close trading statement, Roland Head pointed to its attractive 7% dividend, which should remain well-covered, and he believes that on top of that extra income, investors should expect to see an acceptable capital return.

6. Greene King
In for a third visit this month, perhaps unsurprisingly picking a boozer, Cliff D'Arcy turned his attention to Greene King, which has reported a decent set of results. While some of its competitors have struggled with hefty debt levels, Greene King has kept sales and profits rising and is managing its expansion pretty well. With a forward price-to-earnings ratio of around 10, it looks like there's potential for growth there.

7. Randgold Resources
An FTSE 100 gold miner operating in a country wracked by a military coup and a Tuareg uprising? That's what Tony Reading has picked this month, after political turmoil in Mali knocked 20% off the value of Randgold Resources' shares. Tony recognizes it as one for the brave, but he has confidence in the long-term prospects for miners and sees this as a shorter-term buying opportunity.

8. Rank Group
Sometimes an unusual valuation measure makes us sit up and take notice of a company, and that's exactly what happened when Tony Luckett noticed Rank Group on a lowly P/E ratio of just three. Sure, that is based on some big one-off items in its accounts, and an underlying figure of about 11 is more reasonable, but Tony reckons that "gambling is still a decent business to invest in."

9. e2v Technologies
Malcolm Wheatley has had e2v Technologies on his watch list for a while, and he took a closer look after the strangely named company gave us a trading update. With encouraging news of turnover growth and strong margins, coupled with a lower valuation than its peers, Malcolm sees the firm -- which used to be known as Marconi Applied Technologies -- as a technology share with a decent upside.

10. Punt of the month
With a market capitalization of only 25 million, the AIM-listed New World Oil and Gas is our April punt from David Holding. As he says, it's pretty hit and miss deciding which small oil-exploration companies will find the paydirt, but all we can do is weigh up the risks against the potential. And after having a closer look, David reckons this one might be worth a shot.

What next?
Don't rush out and buy any of these shares solely on our writers' say-so, because they're just ideas to get you started. Instead, take them as starting points for your own research, and only buy shares if you're personally satisfied that you're getting a bargain.

And if you're looking for an alternative to buying individual companies, Harvey Jones has taken a look at the best-selling exchange-traded funds for the first three months of the year. Some are a bit risky, but there are some pretty safe bets in there as well.

See you same time next month with another set of investment ideas.

If you're looking for more share ideas with promising long-term potential, sign up for Motley Fool Share Advisor free for 30 days and get immediate access to all of our research and recommendations. You have no obligation to subscribe.

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