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An important part of running any investment portfolio, I reckon, is not spending too much of your life on it. You should keep up with important news, but don't spend too long poring over the financial pages every morning -- balance is what is needed.

So, has there been any important news for us of late? Indeed there has:

Vodafone
The big news at Vodafone Group (VOD 0.69%) of late is that the mobile telecoms giant has approached Germany's largest cable operator Kabel Deutschland Holding with a view to possibly making an offer for the company. Although Vodafone itself didn't provide us with any details, Kabel Deutschland has a market cap of more than 7 billion euros, and Bloomberg reported an offer of 81-82 euros per share -- not enough, apparently, to even pique the German firm's interest.

The Vodafone share price actually dropped 11 pence on the day to end on 181 pence, so the market wasn't impressed. Too big a target? A distraction from the Verizon business? We'll have to Hold and see. The price today? Down a bit further on 179 pence, and just 5.6% up since we bought at 168.5 pence.

Tesco
Tesco (TSCO 1.68%) brought us a first-quarter update on 5 June, reporting a 2.7% rise in group sales, excluding petrol, with improving like-for-like sales in most categories of foods -- although in the U.K., things are still tough. The company's online grocery continues to lead the market with further outperformance.

The downside lies with Tesco's non-food products, which are not doing as well as hoped -- but there is a focus on improving sales of general merchandise.

Disappointingly for us, the Tesco share price has fallen of late, from a 52-week high of 388 pence, to today's price of 331 pence -- but that's still 8.6% up on our purchase price of 305.5 pence.

Tesco is still very much a Hold.

GlaxoSmithKline
On Tuesday, GlaxoSmithKline (GSK 0.59%) announced it has received an offer for its thrombosis brands and the associated manufacturing site at Notre-Dame de Bondeville, in France. The potential buyer is Aspen Global, a subsidiary of South Africa's Aspen Pharmacare Holdings. We do not yet know the terms of the offer, but the two key drugs involved, Arixtra and Fraxiparine, generated sales of 400 million pounds last year.

According to the announcement, a sale would be "aligned to GSK's strategy of focusing on products with the most growth potential and the delivery of its pipeline."

The punters, however, seem unimpressed, and the share price has fallen 72 pence, to 1,606 pence, from Monday's close of 1,686 pence. But at least it's 11% up on our purchase price of 1440.5 pence almost exactly a year ago.

With earnings growth, and a dividend yield of 4.5% expected, this is another Hold.

Rio Tinto
Our investment in Rio Tinto (RIO -1.47%) has not been a great success in the short term, with the price having dropped 11% from our purchase price of 3,048 pence, to 2,711 pence today -- but the whole sector has been suffering from a slowdown in Chinese growth.

But what news? On 13 June, Rio told us it has agreed to sell its Eagle nickel-copper project in Michigan to Lundin Mining for a cash deal estimated to be worth $325 million. The sale includes the mine itself and the attached mill.

My rating on Rio Tinto now? Well, with a forward price-to-earnings ratio of only eight, and a forecast dividend yield (which should be thrice-covered) of 4.2%, it'll be no surprise that I still rate Rio as a firm Hold -- I really don't care about cyclical downturns.

No regrets!
Another bit of good advice I try to follow is to never rue your past decisions -- learn from them, certainly, but put them swiftly behind you and move on.

I was reminded of this after I dumped engineering consultant WS Atkins (LSE: ATK) from the portfolio's watchlist on June 12. And the very next day, the firm announced a 10% rise in underlying full-year earnings per share, sending the price up 12% to today's 979 pence. Oh well.

Finally, my idea of the kind of shares that should make up the core of a beginner's portfolio is the same as my choice for an ISA, or a retirement portfolio -- or, in fact, any portfolio. I'd start with good strong companies that should stand the test of time and potentially reward you for decades.

Not surprisingly, the Fool's top analysts think similarly, and they have put together a special report detailing five blue-chip shares that I think would be ideal for anyone at the start of his or her investing career.

But it will only be available for a limited period, so click here to get your hands on these great ideas that could start you on the road to long-term riches.

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